diff --git a/Marlin/src/HAL/AVR/HAL.h b/Marlin/src/HAL/AVR/HAL.h
index b606d0c23..ce15ed29f 100644
--- a/Marlin/src/HAL/AVR/HAL.h
+++ b/Marlin/src/HAL/AVR/HAL.h
@@ -120,6 +120,8 @@ void HAL_init();
 inline void HAL_clear_reset_source() { MCUSR = 0; }
 inline uint8_t HAL_get_reset_source() { return MCUSR; }
 
+inline void HAL_reboot() {}  // reboot the board or restart the bootloader
+
 #pragma GCC diagnostic push
 #pragma GCC diagnostic ignored "-Wunused-function"
 extern "C" {
diff --git a/Marlin/src/HAL/DUE/HAL.h b/Marlin/src/HAL/DUE/HAL.h
index dbb84e2ac..f0650e6df 100644
--- a/Marlin/src/HAL/DUE/HAL.h
+++ b/Marlin/src/HAL/DUE/HAL.h
@@ -105,6 +105,8 @@ void sei();                     // Enable interrupts
 void HAL_clear_reset_source();  // clear reset reason
 uint8_t HAL_get_reset_source(); // get reset reason
 
+inline void HAL_reboot() {}  // reboot the board or restart the bootloader
+
 //
 // ADC
 //
diff --git a/Marlin/src/HAL/ESP32/HAL.h b/Marlin/src/HAL/ESP32/HAL.h
index aa3bcc775..81a9a0e59 100644
--- a/Marlin/src/HAL/ESP32/HAL.h
+++ b/Marlin/src/HAL/ESP32/HAL.h
@@ -96,6 +96,8 @@ void HAL_clear_reset_source();
 // reset reason
 uint8_t HAL_get_reset_source();
 
+inline void HAL_reboot() {}  // reboot the board or restart the bootloader
+
 void _delay_ms(int delay);
 
 #pragma GCC diagnostic push
diff --git a/Marlin/src/HAL/LINUX/HAL.h b/Marlin/src/HAL/LINUX/HAL.h
index 778ba2db4..2e545e03d 100644
--- a/Marlin/src/HAL/LINUX/HAL.h
+++ b/Marlin/src/HAL/LINUX/HAL.h
@@ -101,6 +101,8 @@ uint16_t HAL_adc_get_result();
 inline void HAL_clear_reset_source(void) {}
 inline uint8_t HAL_get_reset_source(void) { return RST_POWER_ON; }
 
+inline void HAL_reboot() {}  // reboot the board or restart the bootloader
+
 /* ---------------- Delay in cycles */
 FORCE_INLINE static void DELAY_CYCLES(uint64_t x) {
   Clock::delayCycles(x);
diff --git a/Marlin/src/HAL/LPC1768/HAL.h b/Marlin/src/HAL/LPC1768/HAL.h
index 3118aed1b..cb637e715 100644
--- a/Marlin/src/HAL/LPC1768/HAL.h
+++ b/Marlin/src/HAL/LPC1768/HAL.h
@@ -200,6 +200,8 @@ void set_pwm_duty(const pin_t pin, const uint16_t v, const uint16_t v_size=255,
 void HAL_clear_reset_source(void);
 uint8_t HAL_get_reset_source(void);
 
+inline void HAL_reboot() {}  // reboot the board or restart the bootloader
+
 // Add strcmp_P if missing
 #ifndef strcmp_P
   #define strcmp_P(a, b) strcmp((a), (b))
diff --git a/Marlin/src/HAL/SAMD51/HAL.h b/Marlin/src/HAL/SAMD51/HAL.h
index 7fd826a1b..abc6c04a6 100644
--- a/Marlin/src/HAL/SAMD51/HAL.h
+++ b/Marlin/src/HAL/SAMD51/HAL.h
@@ -88,6 +88,8 @@ typedef int8_t pin_t;
 void HAL_clear_reset_source();  // clear reset reason
 uint8_t HAL_get_reset_source(); // get reset reason
 
+inline void HAL_reboot() {}  // reboot the board or restart the bootloader
+
 //
 // ADC
 //
diff --git a/Marlin/src/HAL/STM32/HAL.h b/Marlin/src/HAL/STM32/HAL.h
index 37919102e..a1f7515d6 100644
--- a/Marlin/src/HAL/STM32/HAL.h
+++ b/Marlin/src/HAL/STM32/HAL.h
@@ -134,6 +134,8 @@ void HAL_clear_reset_source();
 // Reset reason
 uint8_t HAL_get_reset_source();
 
+inline void HAL_reboot() {}  // reboot the board or restart the bootloader
+
 void _delay_ms(const int delay);
 
 extern "C" char* _sbrk(int incr);
diff --git a/Marlin/src/HAL/STM32F1/HAL.h b/Marlin/src/HAL/STM32F1/HAL.h
index 5c03593eb..c10dea0ea 100644
--- a/Marlin/src/HAL/STM32F1/HAL.h
+++ b/Marlin/src/HAL/STM32F1/HAL.h
@@ -185,6 +185,8 @@ void HAL_clear_reset_source();
 // Reset reason
 uint8_t HAL_get_reset_source();
 
+inline void HAL_reboot() {}  // reboot the board or restart the bootloader
+
 void _delay_ms(const int delay);
 
 #pragma GCC diagnostic push
diff --git a/Marlin/src/HAL/STM32_F4_F7/HAL.h b/Marlin/src/HAL/STM32_F4_F7/HAL.h
index 88e48f0fa..00a65de79 100644
--- a/Marlin/src/HAL/STM32_F4_F7/HAL.h
+++ b/Marlin/src/HAL/STM32_F4_F7/HAL.h
@@ -142,6 +142,8 @@ void HAL_clear_reset_source();
 // Reset reason
 uint8_t HAL_get_reset_source();
 
+inline void HAL_reboot() {}  // reboot the board or restart the bootloader
+
 void _delay_ms(const int delay);
 
 /*
diff --git a/Marlin/src/HAL/TEENSY31_32/HAL.h b/Marlin/src/HAL/TEENSY31_32/HAL.h
index b434b9de7..5fc65680d 100644
--- a/Marlin/src/HAL/TEENSY31_32/HAL.h
+++ b/Marlin/src/HAL/TEENSY31_32/HAL.h
@@ -93,6 +93,8 @@ void HAL_clear_reset_source();
 // Get the reason for the reset
 uint8_t HAL_get_reset_source();
 
+inline void HAL_reboot() {}  // reboot the board or restart the bootloader
+
 FORCE_INLINE void _delay_ms(const int delay_ms) { delay(delay_ms); }
 
 #pragma GCC diagnostic push
diff --git a/Marlin/src/HAL/TEENSY35_36/HAL.h b/Marlin/src/HAL/TEENSY35_36/HAL.h
index f454e7af5..30db40dfa 100644
--- a/Marlin/src/HAL/TEENSY35_36/HAL.h
+++ b/Marlin/src/HAL/TEENSY35_36/HAL.h
@@ -99,6 +99,8 @@ void HAL_clear_reset_source();
 // Reset reason
 uint8_t HAL_get_reset_source();
 
+inline void HAL_reboot() {}  // reboot the board or restart the bootloader
+
 FORCE_INLINE void _delay_ms(const int delay_ms) { delay(delay_ms); }
 
 #pragma GCC diagnostic push
diff --git a/Marlin/src/core/macros.h b/Marlin/src/core/macros.h
index 5fc108101..72644b195 100644
--- a/Marlin/src/core/macros.h
+++ b/Marlin/src/core/macros.h
@@ -215,6 +215,7 @@
 #define WITHIN(N,L,H)       ((N) >= (L) && (N) <= (H))
 #define NUMERIC(a)          WITHIN(a, '0', '9')
 #define DECIMAL(a)          (NUMERIC(a) || a == '.')
+#define HEXCHR(a)           (NUMERIC(a) ? (a) - '0' : WITHIN(a, 'a', 'f') ? ((a) - 'a' + 10)  : WITHIN(a, 'A', 'F') ? ((a) - 'A' + 10) : -1)
 #define NUMERIC_SIGNED(a)   (NUMERIC(a) || (a) == '-' || (a) == '+')
 #define DECIMAL_SIGNED(a)   (DECIMAL(a) || (a) == '-' || (a) == '+')
 #define COUNT(a)            (sizeof(a)/sizeof(*a))
diff --git a/Marlin/src/feature/e_parser.h b/Marlin/src/feature/e_parser.h
index 8d11463ec..085cbd4ea 100644
--- a/Marlin/src/feature/e_parser.h
+++ b/Marlin/src/feature/e_parser.h
@@ -88,10 +88,8 @@ public:
 
       case EP_N:
         switch (c) {
-          case '0': case '1': case '2':
-          case '3': case '4': case '5':
-          case '6': case '7': case '8':
-          case '9': case '-': case ' ':   break;
+          case '0' ... '9':
+          case '-': case ' ':   break;
           case 'M': state = EP_M;      break;
           default:  state = EP_IGNORE;
         }
@@ -153,10 +151,7 @@ public:
       case EP_M876S:
         switch (c) {
           case ' ': break;
-          case '0': case '1': case '2':
-          case '3': case '4': case '5':
-          case '6': case '7': case '8':
-          case '9':
+          case '0' ... '9':
             state = EP_M876SN;
             M876_reason = (uint8_t)(c - '0');
             break;
diff --git a/Marlin/src/gcode/control/T.cpp b/Marlin/src/gcode/control/T.cpp
index 729f7f222..d95e60ff8 100644
--- a/Marlin/src/gcode/control/T.cpp
+++ b/Marlin/src/gcode/control/T.cpp
@@ -46,7 +46,7 @@
  *   Tx   Same as T?, but nozzle doesn't have to be preheated. Tc requires a preheated nozzle to finish filament load.
  *   Tc   Load to nozzle after filament was prepared by Tc and nozzle is already heated.
  */
-void GcodeSuite::T(const uint8_t tool_index) {
+void GcodeSuite::T(const int8_t tool_index) {
 
   DEBUG_SECTION(log_T, "T", DEBUGGING(LEVELING));
   if (DEBUGGING(LEVELING)) DEBUG_ECHOLNPAIR("...(", tool_index, ")");
diff --git a/Marlin/src/gcode/gcode.cpp b/Marlin/src/gcode/gcode.cpp
index 1de54259b..3d70b7c85 100644
--- a/Marlin/src/gcode/gcode.cpp
+++ b/Marlin/src/gcode/gcode.cpp
@@ -923,6 +923,10 @@ void GcodeSuite::process_parsed_command(const bool no_ok/*=false*/) {
 
     case 'T': T(parser.codenum); break;                           // Tn: Tool Change
 
+    #if ENABLED(MARLIN_DEV_MODE)
+      case 'D': D(parser.codenum); break;                         // Dn: Debug codes
+    #endif
+
     default:
       #if ENABLED(WIFI_CUSTOM_COMMAND)
         if (wifi_custom_command(parser.command_ptr)) break;
diff --git a/Marlin/src/gcode/gcode.h b/Marlin/src/gcode/gcode.h
index 026083bcf..f21b7f89b 100644
--- a/Marlin/src/gcode/gcode.h
+++ b/Marlin/src/gcode/gcode.h
@@ -285,6 +285,7 @@
  * M995 - Touch screen calibration for TFT display
  * M997 - Perform in-application firmware update
  * M999 - Restart after being stopped by error
+ * D... - Custom Development G-code. Add hooks to 'gcode_D.cpp' for developers to test features. (Requires MARLIN_DEV_MODE)
  *
  * "T" Codes
  *
@@ -408,6 +409,8 @@ public:
 
 private:
 
+  TERN_(MARLIN_DEV_MODE, static void D(const int16_t dcode));
+
   static void G0_G1(TERN_(HAS_FAST_MOVES, const bool fast_move=false));
 
   TERN_(ARC_SUPPORT, static void G2_G3(const bool clockwise));
@@ -882,7 +885,7 @@ private:
 
   TERN_(CONTROLLER_FAN_EDITABLE, static void M710());
 
-  static void T(const uint8_t tool_index);
+  static void T(const int8_t tool_index);
 
 };
 
diff --git a/Marlin/src/gcode/gcode_d.cpp b/Marlin/src/gcode/gcode_d.cpp
new file mode 100644
index 000000000..4bc3b6c6c
--- /dev/null
+++ b/Marlin/src/gcode/gcode_d.cpp
@@ -0,0 +1,173 @@
+/**
+ * Marlin 3D Printer Firmware
+ * Copyright (c) 2020 MarlinFirmware [https://github.com/MarlinFirmware/Marlin]
+ *
+ * Based on Sprinter and grbl.
+ * Copyright (c) 2011 Camiel Gubbels / Erik van der Zalm
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ *
+ */
+#include "../inc/MarlinConfigPre.h"
+
+#if ENABLED(MARLIN_DEV_MODE)
+
+  #include "gcode.h"
+  #include "../module/settings.h"
+  #include "../libs/hex_print.h"
+  #include "../HAL/shared/eeprom_if.h"
+
+  /**
+   * Dn: G-code for development and testing
+   *
+   * See https://reprap.org/wiki/G-code#D:_Debug_codes
+   *
+   * Put whatever else you need here to test ongoing development.
+   */
+  void GcodeSuite::D(const int16_t dcode) {
+    switch (dcode) {
+
+      case -1:
+        for (;;); // forever
+
+      case 0:
+        HAL_reboot();
+        break;
+
+      case 1: {
+        // Zero or pattern-fill the EEPROM data
+        #if ENABLED(EEPROM_SETTINGS)
+          persistentStore.access_start();
+          size_t total = persistentStore.capacity();
+          int pos = 0;
+          const uint8_t value = 0x0;
+          while(total--) {
+            persistentStore.write_data(pos, &value, 1);
+          }
+          persistentStore.access_finish();
+        #else
+          settings.reset();
+          settings.save();
+        #endif
+        HAL_reboot();
+      } break;
+
+      case 2: { // D2 Read / Write SRAM
+        #define SRAM_SIZE 8192
+        uint8_t *pointer = parser.hex_adr_val('A');
+        uint16_t len = parser.ushortval('C', 1);
+        uintptr_t addr = (uintptr_t)pointer;
+        NOMORE(addr, (size_t)(SRAM_SIZE - 1));
+        NOMORE(len, SRAM_SIZE - addr);
+        if (parser.seenval('X')) {
+          // Write the hex bytes after the X
+          uint16_t val = parser.hex_val('X');
+          while (len--) {
+            *pointer = val;
+            pointer++;
+          }
+        }
+        else {
+          while (len--) print_hex_byte(*(pointer++));
+          SERIAL_EOL();
+        }
+      } break;
+
+      case 3: { // D3 Read / Write EEPROM
+        uint8_t *pointer = parser.hex_adr_val('A');
+        uint16_t len = parser.ushortval('C', 1);
+        uintptr_t addr = (uintptr_t)pointer;
+        #ifndef MARLIN_EEPROM_SIZE
+          #define MARLIN_EEPROM_SIZE size_t(E2END + 1)
+        #endif
+        NOMORE(addr, (size_t)(MARLIN_EEPROM_SIZE - 1));
+        NOMORE(len, MARLIN_EEPROM_SIZE - addr);
+        if (parser.seenval('X')) {
+          uint16_t val = parser.hex_val('X');
+          #if ENABLED(EEPROM_SETTINGS)
+            persistentStore.access_start();
+            while(len--) {
+              int pos = 0;
+              persistentStore.write_data(pos, (uint8_t *)&val, sizeof(val));
+            }
+            SERIAL_EOL();
+            persistentStore.access_finish();
+          #else
+            SERIAL_ECHOLN("NO EEPROM");
+          #endif
+        }
+        else {
+          while (len--) {
+            // Read bytes from EEPROM
+            #if ENABLED(EEPROM_SETTINGS)
+              persistentStore.access_start();
+              uint8_t val;
+              while(len--) {
+                int pos = 0;
+                if (!persistentStore.read_data(pos, (uint8_t *)&val, sizeof(val))) {
+                  print_hex_byte(val);
+                }
+              }
+              SERIAL_EOL();
+              persistentStore.access_finish();
+            #else
+              SERIAL_ECHOLN("NO EEPROM");
+            #endif
+          }
+          SERIAL_EOL();
+        }
+      } break;
+
+      case 4: { // D4 Read / Write PIN
+        // const uint8_t pin = parser.byteval('P');
+        // const bool is_out = parser.boolval('F'),
+        //            val = parser.byteval('V', LOW);
+        if (parser.seenval('X')) {
+          // TODO: Write the hex bytes after the X
+          //while (len--) {
+          //}
+        }
+        else {
+          // while (len--) {
+            // TODO: Read bytes from EEPROM
+            // print_hex_byte(eeprom_read_byte(*(adr++));
+          // }
+          SERIAL_EOL();
+        }
+      } break;
+
+      case 5: { // D4 Read / Write onboard Flash
+        #define FLASH_SIZE 1024
+        uint8_t *pointer = parser.hex_adr_val('A');
+        uint16_t len = parser.ushortval('C', 1);
+        uintptr_t addr = (uintptr_t)pointer;
+        NOMORE(addr, (size_t)(FLASH_SIZE - 1));
+        NOMORE(len, FLASH_SIZE - addr);
+        if (parser.seenval('X')) {
+          // TODO: Write the hex bytes after the X
+          //while (len--) {
+          //}
+        }
+        else {
+          // while (len--) {
+            // TODO: Read bytes from EEPROM
+            // print_hex_byte(eeprom_read_byte(adr++));
+          // }
+          SERIAL_EOL();
+        }
+      } break;
+    }
+  }
+
+#endif
diff --git a/Marlin/src/gcode/parser.cpp b/Marlin/src/gcode/parser.cpp
index b3172e7f6..9c5085b97 100644
--- a/Marlin/src/gcode/parser.cpp
+++ b/Marlin/src/gcode/parser.cpp
@@ -147,22 +147,15 @@ void GCodeParser::parse(char *p) {
     starpos[1] = '\0';
   }
 
-  #if ENABLED(GCODE_MOTION_MODES)
-    #if ENABLED(ARC_SUPPORT)
-      #define GTOP 3
-    #else
-      #define GTOP 1
-    #endif
+  #if ANY(MARLIN_DEV_MODE, SWITCHING_TOOLHEAD, MAGNETIC_SWITCHING_TOOLHEAD, ELECTROMAGNETIC_SWITCHING_TOOLHEAD)
+    #define SIGNED_CODENUM 1
   #endif
 
   // Bail if the letter is not G, M, or T
   // (or a valid parameter for the current motion mode)
   switch (letter) {
 
-    case 'G': case 'M': case 'T':
-    #if ENABLED(CANCEL_OBJECTS)
-      case 'O':
-    #endif
+    case 'G': case 'M': case 'T': TERN_(MARLIN_DEV_MODE, case 'D':)
       // Skip spaces to get the numeric part
       while (*p == ' ') p++;
 
@@ -178,22 +171,33 @@ void GCodeParser::parse(char *p) {
       #endif
 
       // Bail if there's no command code number
-      if (!NUMERIC(*p)) return;
+      if (!TERN(SIGNED_CODENUM, NUMERIC_SIGNED(*p), NUMERIC(*p))) return;
 
       // Save the command letter at this point
       // A '?' signifies an unknown command
       command_letter = letter;
 
-      // Get the code number - integer digits only
-      codenum = 0;
-      do { codenum *= 10, codenum += *p++ - '0'; } while (NUMERIC(*p));
+      {
+        #if ENABLED(SIGNED_CODENUM)
+          int sign = 1; // Allow for a negative code like D-1 or T-1
+          if (*p == '-') { sign = -1; ++p; }
+        #endif
+
+        // Get the code number - integer digits only
+        codenum = 0;
+
+        do { codenum = codenum * 10 + *p++ - '0'; } while (NUMERIC(*p));
+
+        // Apply the sign, if any
+        TERN_(SIGNED_CODENUM, codenum *= sign);
+      }
 
       // Allow for decimal point in command
       #if ENABLED(USE_GCODE_SUBCODES)
         if (*p == '.') {
           p++;
           while (NUMERIC(*p))
-          subcode *= 10, subcode += *p++ - '0';
+            subcode = subcode * 10 + *p++ - '0';
         }
       #endif
 
@@ -201,11 +205,8 @@ void GCodeParser::parse(char *p) {
       while (*p == ' ') p++;
 
       #if ENABLED(GCODE_MOTION_MODES)
-        if (letter == 'G' && (codenum <= GTOP || codenum == 5
-                                #if ENABLED(G38_PROBE_TARGET)
-                                  || codenum == 38
-                                #endif
-                             )
+        if (letter == 'G'
+          && (codenum <= TERN(ARC_SUPPORT, 3, 1) || codenum == 5 || TERN0(G38_PROBE_TARGET, codenum == 38))
         ) {
           motion_mode_codenum = codenum;
           TERN_(USE_GCODE_SUBCODES, motion_mode_subcode = subcode);
@@ -216,12 +217,12 @@ void GCodeParser::parse(char *p) {
 
     #if ENABLED(GCODE_MOTION_MODES)
       #if ENABLED(ARC_SUPPORT)
-        case 'I': case 'J': case 'R':
+        case 'I' ... 'J': case 'R':
           if (motion_mode_codenum != 2 && motion_mode_codenum != 3) return;
       #endif
-      case 'P': case 'Q':
+      case 'P' ... 'Q':
         if (motion_mode_codenum != 5) return;
-      case 'X': case 'Y': case 'Z': case 'E': case 'F':
+      case 'X' ... 'Z': case 'E' ... 'F':
         if (motion_mode_codenum < 0) return;
         command_letter = 'G';
         codenum = motion_mode_codenum;
@@ -247,7 +248,7 @@ void GCodeParser::parse(char *p) {
     #if ENABLED(EXPECTED_PRINTER_CHECK)
       case 16:
     #endif
-    case 23: case 28: case 30: case 33: case 117: case 118: case 928:
+    case 23: case 28: case 30: case 117 ... 118: case 928:
       string_arg = unescape_string(p);
       return;
     default: break;
diff --git a/Marlin/src/gcode/parser.h b/Marlin/src/gcode/parser.h
index eb614c33b..42b85ca27 100644
--- a/Marlin/src/gcode/parser.h
+++ b/Marlin/src/gcode/parser.h
@@ -114,6 +114,11 @@ public:
     return valid_signless(p) || ((p[0] == '-' || p[0] == '+') && valid_signless(&p[1])); // [-+]?.?[0-9]
   }
 
+  FORCE_INLINE static bool valid_number(const char * const p) {
+    // TODO: With MARLIN_DEV_MODE allow HEX values starting with "x"
+    return valid_float(p);
+  }
+
   #if ENABLED(FASTER_GCODE_PARSER)
 
     FORCE_INLINE static bool valid_int(const char * const p) {
@@ -142,8 +147,12 @@ public:
       if (ind >= COUNT(param)) return false; // Only A-Z
       const bool b = TEST32(codebits, ind);
       if (b) {
-        char * const ptr = command_ptr + param[ind];
-        value_ptr = param[ind] && valid_float(ptr) ? ptr : nullptr;
+        if (param[ind]) {
+          char * const ptr = command_ptr + param[ind];
+          value_ptr = valid_number(ptr) ? ptr : nullptr;
+        }
+        else
+          value_ptr = nullptr;
       }
       return b;
     }
@@ -198,7 +207,7 @@ public:
     static inline bool seen(const char c) {
       char *p = strgchr(command_args, c);
       const bool b = !!p;
-      if (b) value_ptr = valid_float(&p[1]) ? &p[1] : nullptr;
+      if (b) value_ptr = valid_number(&p[1]) ? &p[1] : nullptr;
       return b;
     }
 
@@ -401,6 +410,25 @@ public:
   static inline float    linearval(const char c, const float dval=0)    { return seenval(c) ? value_linear_units() : dval; }
   static inline float    celsiusval(const char c, const float dval=0)   { return seenval(c) ? value_celsius()      : dval; }
 
+  #if ENABLED(MARLIN_DEV_MODE)
+
+    static inline uint8_t* hex_adr_val(const char c, uint8_t * const dval=nullptr) {
+      if (!seen(c) || *value_ptr != 'x') return dval;
+      uint8_t *out = nullptr;
+      for (char *vp = value_ptr + 1; HEXCHR(*vp) >= 0; vp++)
+        out = (uint8_t*)((uintptr_t(out) << 8) | HEXCHR(*vp));
+      return out;
+    }
+
+    static inline uint16_t hex_val(const char c, uint16_t const dval=0) {
+      if (!seen(c) || *value_ptr != 'x') return dval;
+      uint16_t out = 0;
+      for (char *vp = value_ptr + 1; HEXCHR(*vp) >= 0; vp++)
+        out = ((out) << 8) | HEXCHR(*vp);
+      return out;
+    }
+
+  #endif
 };
 
 extern GCodeParser parser;
diff --git a/Marlin/src/lcd/ultralcd.cpp b/Marlin/src/lcd/ultralcd.cpp
index de534e402..92dd63389 100644
--- a/Marlin/src/lcd/ultralcd.cpp
+++ b/Marlin/src/lcd/ultralcd.cpp
@@ -123,11 +123,15 @@ constexpr uint8_t epps = ENCODER_PULSES_PER_STEP;
 #include "lcdprint.h"
 
 #include "../sd/cardreader.h"
-#include "../module/settings.h"
+
 #include "../module/temperature.h"
 #include "../module/planner.h"
 #include "../module/motion.h"
 
+#if HAS_LCD_MENU
+  #include "../module/settings.h"
+#endif
+
 #if ENABLED(AUTO_BED_LEVELING_UBL)
   #include "../feature/bedlevel/bedlevel.h"
 #endif