Expose DISABLE_M503 option as a test option

Marlin/Configuration.h

 //#define EEPROM_SETTINGS
 
 #if ENABLED(EEPROM_SETTINGS)
-  // To disable EEPROM Serial responses and decrease program space by ~1700 byte: comment this out:
-  #define EEPROM_CHITCHAT // Please keep turned on if you can.
+  //#define DISABLE_M503  // Saves ~2700 bytes of PROGMEM. Disable for release!
+  #define EEPROM_CHITCHAT // Print a report on M500. Please keep turned on.
 #endif
 
 //

Marlin/Marlin_main.cpp

   (void)settings.reset();
 }
 
-/**
- * M503: print settings currently in memory
- */
-inline void gcode_M503() {
-  (void)settings.report(!parser.boolval('S', true));
-}
+#if DISABLED(DISABLE_M503)
+  /**
+   * M503: print settings currently in memory
+   */
+  inline void gcode_M503() {
+    (void)settings.report(!parser.boolval('S', true));
+  }
+#endif
 
 #if ENABLED(ABORT_ON_ENDSTOP_HIT_FEATURE_ENABLED)
 
       case 502: // M502: Revert to default settings
         gcode_M502();
         break;
-      case 503: // M503: print settings currently in memory
-        gcode_M503();
-        break;
+
+      #if DISABLED(DISABLE_M503)
+        case 503: // M503: print settings currently in memory
+          gcode_M503();
+          break;
+      #endif
 
       #if ENABLED(ABORT_ON_ENDSTOP_HIT_FEATURE_ENABLED)
         case 540: // M540: Set abort on endstop hit for SD printing

Marlin/configuration_store.cpp

       #endif
     }
 
-    #if ENABLED(EEPROM_CHITCHAT)
+    #if ENABLED(EEPROM_CHITCHAT) && DISABLED(DISABLE_M503)
       report();
     #endif
 

Marlin/configuration_store.h

       static void report(bool forReplay=false);
     #else
       FORCE_INLINE
-      static void report(bool forReplay=false) { }
+      static void report(bool forReplay=false) { UNUSED(forReplay); }
     #endif
 
   private:

Marlin/example_configurations/Anet/A6/Configuration.h

 #define EEPROM_SETTINGS
 
 #if ENABLED(EEPROM_SETTINGS)
-  // To disable EEPROM Serial responses and decrease program space by ~1700 byte: comment this out:
-  #define EEPROM_CHITCHAT // Please keep turned on if you can.
+  //#define DISABLE_M503  // Saves ~2700 bytes of PROGMEM. Disable for release!
+  #define EEPROM_CHITCHAT // Print a report on M500. Please keep turned on.
 #endif
 
 //

Marlin/example_configurations/Anet/A8/Configuration.h

 #define EEPROM_SETTINGS
 
 #if ENABLED(EEPROM_SETTINGS)
-  // To disable EEPROM Serial responses and decrease program space by ~1700 byte: comment this out:
-  #define EEPROM_CHITCHAT // Please keep turned on if you can.
+  //#define DISABLE_M503  // Saves ~2700 bytes of PROGMEM. Disable for release!
+  #define EEPROM_CHITCHAT // Print a report on M500. Please keep turned on.
 #endif
 
 //

Marlin/example_configurations/CL-260/Configuration.h

 //#define EEPROM_SETTINGS
 
 #if ENABLED(EEPROM_SETTINGS)
-  // To disable EEPROM Serial responses and decrease program space by ~1700 byte: comment this out:
-  #define EEPROM_CHITCHAT // Please keep turned on if you can.
+  //#define DISABLE_M503  // Saves ~2700 bytes of PROGMEM. Disable for release!
+  #define EEPROM_CHITCHAT // Print a report on M500. Please keep turned on.
 #endif
 
 //

Marlin/example_configurations/Cartesio/Configuration.h

 //#define EEPROM_SETTINGS
 
 #if ENABLED(EEPROM_SETTINGS)
-  // To disable EEPROM Serial responses and decrease program space by ~1700 byte: comment this out:
-  #define EEPROM_CHITCHAT // Please keep turned on if you can.
+  //#define DISABLE_M503  // Saves ~2700 bytes of PROGMEM. Disable for release!
+  #define EEPROM_CHITCHAT // Print a report on M500. Please keep turned on.
 #endif
 
 //

Marlin/example_configurations/Felix/Configuration.h

 //#define EEPROM_SETTINGS
 
 #if ENABLED(EEPROM_SETTINGS)
-  // To disable EEPROM Serial responses and decrease program space by ~1700 byte: comment this out:
-  #define EEPROM_CHITCHAT // Please keep turned on if you can.
+  //#define DISABLE_M503  // Saves ~2700 bytes of PROGMEM. Disable for release!
+  #define EEPROM_CHITCHAT // Print a report on M500. Please keep turned on.
 #endif
 
 //

Marlin/example_configurations/Felix/DUAL/Configuration.h

 //#define EEPROM_SETTINGS
 
 #if ENABLED(EEPROM_SETTINGS)
-  // To disable EEPROM Serial responses and decrease program space by ~1700 byte: comment this out:
-  #define EEPROM_CHITCHAT // Please keep turned on if you can.
+  //#define DISABLE_M503  // Saves ~2700 bytes of PROGMEM. Disable for release!
+  #define EEPROM_CHITCHAT // Print a report on M500. Please keep turned on.
 #endif
 
 //

Marlin/example_configurations/FolgerTech-i3-2020/Configuration.h

 #define EEPROM_SETTINGS
 
 #if ENABLED(EEPROM_SETTINGS)
-  // To disable EEPROM Serial responses and decrease program space by ~1700 byte: comment this out:
-  #define EEPROM_CHITCHAT // Please keep turned on if you can.
+  //#define DISABLE_M503  // Saves ~2700 bytes of PROGMEM. Disable for release!
+  #define EEPROM_CHITCHAT // Print a report on M500. Please keep turned on.
 #endif
 
 //

Marlin/example_configurations/Hephestos/Configuration.h

 //#define EEPROM_SETTINGS
 
 #if ENABLED(EEPROM_SETTINGS)
-  // To disable EEPROM Serial responses and decrease program space by ~1700 byte: comment this out:
-  #define EEPROM_CHITCHAT // Please keep turned on if you can.
+  //#define DISABLE_M503  // Saves ~2700 bytes of PROGMEM. Disable for release!
+  #define EEPROM_CHITCHAT // Print a report on M500. Please keep turned on.
 #endif
 
 //

Marlin/example_configurations/Hephestos_2/Configuration.h

 #define EEPROM_SETTINGS
 
 #if ENABLED(EEPROM_SETTINGS)
-  // To disable EEPROM Serial responses and decrease program space by ~1700 byte: comment this out:
-  #define EEPROM_CHITCHAT // Please keep turned on if you can.
+  //#define DISABLE_M503  // Saves ~2700 bytes of PROGMEM. Disable for release!
+  #define EEPROM_CHITCHAT // Print a report on M500. Please keep turned on.
 #endif
 
 //

Marlin/example_configurations/K8200/Configuration.h

 #define EEPROM_SETTINGS // K8200: uses EEPROM by default
 
 #if ENABLED(EEPROM_SETTINGS)
-  // To disable EEPROM Serial responses and decrease program space by ~1700 byte: comment this out:
-  #define EEPROM_CHITCHAT // Please keep turned on if you can.
+  //#define DISABLE_M503  // Saves ~2700 bytes of PROGMEM. Disable for release!
+  #define EEPROM_CHITCHAT // Print a report on M500. Please keep turned on.
 #endif
 
 //

Marlin/example_configurations/K8400/Configuration.h

 #define EEPROM_SETTINGS
 
 #if ENABLED(EEPROM_SETTINGS)
-  // To disable EEPROM Serial responses and decrease program space by ~1700 byte: comment this out:
-  #define EEPROM_CHITCHAT // Please keep turned on if you can.
+  //#define DISABLE_M503  // Saves ~2700 bytes of PROGMEM. Disable for release!
+  #define EEPROM_CHITCHAT // Print a report on M500. Please keep turned on.
 #endif
 
 //

Marlin/example_configurations/K8400/Dual-head/Configuration.h

 #define EEPROM_SETTINGS
 
 #if ENABLED(EEPROM_SETTINGS)
-  // To disable EEPROM Serial responses and decrease program space by ~1700 byte: comment this out:
-  #define EEPROM_CHITCHAT // Please keep turned on if you can.
+  //#define DISABLE_M503  // Saves ~2700 bytes of PROGMEM. Disable for release!
+  #define EEPROM_CHITCHAT // Print a report on M500. Please keep turned on.
 #endif
 
 //

Marlin/example_configurations/M150/Configuration.h

 #define EEPROM_SETTINGS
 
 #if ENABLED(EEPROM_SETTINGS)
-  // To disable EEPROM Serial responses and decrease program space by ~1700 byte: comment this out:
-  #define EEPROM_CHITCHAT // Please keep turned on if you can.
+  //#define DISABLE_M503  // Saves ~2700 bytes of PROGMEM. Disable for release!
+  #define EEPROM_CHITCHAT // Print a report on M500. Please keep turned on.
 #endif
 
 //

Marlin/example_configurations/RepRapWorld/Megatronics/Configuration.h

 //#define EEPROM_SETTINGS
 
 #if ENABLED(EEPROM_SETTINGS)
-  // To disable EEPROM Serial responses and decrease program space by ~1700 byte: comment this out:
-  #define EEPROM_CHITCHAT // Please keep turned on if you can.
+  //#define DISABLE_M503  // Saves ~2700 bytes of PROGMEM. Disable for release!
+  #define EEPROM_CHITCHAT // Print a report on M500. Please keep turned on.
 #endif
 
 //

Marlin/example_configurations/RigidBot/Configuration.h

 #define EEPROM_SETTINGS
 
 #if ENABLED(EEPROM_SETTINGS)
-  // To disable EEPROM Serial responses and decrease program space by ~1700 byte: comment this out:
-  #define EEPROM_CHITCHAT // Please keep turned on if you can.
+  //#define DISABLE_M503  // Saves ~2700 bytes of PROGMEM. Disable for release!
+  #define EEPROM_CHITCHAT // Print a report on M500. Please keep turned on.
 #endif
 
 //

Marlin/example_configurations/SCARA/Configuration.h

 //#define EEPROM_SETTINGS
 
 #if ENABLED(EEPROM_SETTINGS)
-  // To disable EEPROM Serial responses and decrease program space by ~1700 byte: comment this out:
-  #define EEPROM_CHITCHAT // Please keep turned on if you can.
+  //#define DISABLE_M503  // Saves ~2700 bytes of PROGMEM. Disable for release!
+  #define EEPROM_CHITCHAT // Print a report on M500. Please keep turned on.
 #endif
 
 //

Marlin/example_configurations/TAZ4/Configuration.h

 #define EEPROM_SETTINGS
 
 #if ENABLED(EEPROM_SETTINGS)
-  // To disable EEPROM Serial responses and decrease program space by ~1700 byte: comment this out:
-  #define EEPROM_CHITCHAT // Please keep turned on if you can.
+  //#define DISABLE_M503  // Saves ~2700 bytes of PROGMEM. Disable for release!
+  #define EEPROM_CHITCHAT // Print a report on M500. Please keep turned on.
 #endif
 
 //

Marlin/example_configurations/TinyBoy2/Configuration.h

 #define EEPROM_SETTINGS
 
 #if ENABLED(EEPROM_SETTINGS)
-  // To disable EEPROM Serial responses and decrease program space by ~1700 byte: comment this out:
-  #define EEPROM_CHITCHAT // Please keep turned on if you can.
+  //#define DISABLE_M503  // Saves ~2700 bytes of PROGMEM. Disable for release!
+  #define EEPROM_CHITCHAT // Print a report on M500. Please keep turned on.
 #endif
 
 //

Marlin/example_configurations/WITBOX/Configuration.h

 //#define EEPROM_SETTINGS
 
 #if ENABLED(EEPROM_SETTINGS)
-  // To disable EEPROM Serial responses and decrease program space by ~1700 byte: comment this out:
-  #define EEPROM_CHITCHAT // Please keep turned on if you can.
+  //#define DISABLE_M503  // Saves ~2700 bytes of PROGMEM. Disable for release!
+  #define EEPROM_CHITCHAT // Print a report on M500. Please keep turned on.
 #endif
 
 //

Marlin/example_configurations/adafruit/ST7565/Configuration.h

 //#define EEPROM_SETTINGS
 
 #if ENABLED(EEPROM_SETTINGS)
-  // To disable EEPROM Serial responses and decrease program space by ~1700 byte: comment this out:
-  #define EEPROM_CHITCHAT // Please keep turned on if you can.
+  //#define DISABLE_M503  // Saves ~2700 bytes of PROGMEM. Disable for release!
+  #define EEPROM_CHITCHAT // Print a report on M500. Please keep turned on.
 #endif
 
 //

Marlin/example_configurations/delta/FLSUN/auto_calibrate/Configuration.h

 #define EEPROM_SETTINGS
 
 #if ENABLED(EEPROM_SETTINGS)
-  // To disable EEPROM Serial responses and decrease program space by ~1700 byte: comment this out:
-  #define EEPROM_CHITCHAT // Please keep turned on if you can.
+  //#define DISABLE_M503  // Saves ~2700 bytes of PROGMEM. Disable for release!
+  #define EEPROM_CHITCHAT // Print a report on M500. Please keep turned on.
 #endif
 
 //

Marlin/example_configurations/delta/FLSUN/kossel_mini/Configuration.h

 #define EEPROM_SETTINGS
 
 #if ENABLED(EEPROM_SETTINGS)
-  // To disable EEPROM Serial responses and decrease program space by ~1700 byte: comment this out:
-  #define EEPROM_CHITCHAT // Please keep turned on if you can.
+  //#define DISABLE_M503  // Saves ~2700 bytes of PROGMEM. Disable for release!
+  #define EEPROM_CHITCHAT // Print a report on M500. Please keep turned on.
 #endif
 
 //

Marlin/example_configurations/delta/generic/Configuration.h

 //#define EEPROM_SETTINGS
 
 #if ENABLED(EEPROM_SETTINGS)
-  // To disable EEPROM Serial responses and decrease program space by ~1700 byte: comment this out:
-  #define EEPROM_CHITCHAT // Please keep turned on if you can.
+  //#define DISABLE_M503  // Saves ~2700 bytes of PROGMEM. Disable for release!
+  #define EEPROM_CHITCHAT // Print a report on M500. Please keep turned on.
 #endif
 
 //

Marlin/example_configurations/delta/kossel_mini/Configuration.h

 //#define EEPROM_SETTINGS
 
 #if ENABLED(EEPROM_SETTINGS)
-  // To disable EEPROM Serial responses and decrease program space by ~1700 byte: comment this out:
-  #define EEPROM_CHITCHAT // Please keep turned on if you can.
+  //#define DISABLE_M503  // Saves ~2700 bytes of PROGMEM. Disable for release!
+  #define EEPROM_CHITCHAT // Print a report on M500. Please keep turned on.
 #endif
 
 //

Marlin/example_configurations/delta/kossel_pro/Configuration.h

 //#define EEPROM_SETTINGS
 
 #if ENABLED(EEPROM_SETTINGS)
-  // To disable EEPROM Serial responses and decrease program space by ~1700 byte: comment this out:
-  #define EEPROM_CHITCHAT // Please keep turned on if you can.
+  //#define DISABLE_M503  // Saves ~2700 bytes of PROGMEM. Disable for release!
+  #define EEPROM_CHITCHAT // Print a report on M500. Please keep turned on.
 #endif
 
 //

Marlin/example_configurations/delta/kossel_xl/Configuration.h

 #define EEPROM_SETTINGS
 
 #if ENABLED(EEPROM_SETTINGS)
-  // To disable EEPROM Serial responses and decrease program space by ~1700 byte: comment this out:
-  #define EEPROM_CHITCHAT // Please keep turned on if you can.
+  //#define DISABLE_M503  // Saves ~2700 bytes of PROGMEM. Disable for release!
+  #define EEPROM_CHITCHAT // Print a report on M500. Please keep turned on.
 #endif
 
 //

Marlin/example_configurations/gCreate_gMax1.5+/Configuration.h

 #define EEPROM_SETTINGS
 
 #if ENABLED(EEPROM_SETTINGS)
-  // To disable EEPROM Serial responses and decrease program space by ~1700 byte: comment this out:
-  #define EEPROM_CHITCHAT // Please keep turned on if you can.
+  //#define DISABLE_M503  // Saves ~2700 bytes of PROGMEM. Disable for release!
+  #define EEPROM_CHITCHAT // Print a report on M500. Please keep turned on.
 #endif
 
 //

Marlin/example_configurations/makibox/Configuration.h

 #define EEPROM_SETTINGS
 
 #if ENABLED(EEPROM_SETTINGS)
-  // To disable EEPROM Serial responses and decrease program space by ~1700 byte: comment this out:
-  #define EEPROM_CHITCHAT // Please keep turned on if you can.
+  //#define DISABLE_M503  // Saves ~2700 bytes of PROGMEM. Disable for release!
+  #define EEPROM_CHITCHAT // Print a report on M500. Please keep turned on.
 #endif
 
 //

Marlin/example_configurations/tvrrug/Round2/Configuration.h

 //#define EEPROM_SETTINGS
 
 #if ENABLED(EEPROM_SETTINGS)
-  // To disable EEPROM Serial responses and decrease program space by ~1700 byte: comment this out:
-  #define EEPROM_CHITCHAT // Please keep turned on if you can.
+  //#define DISABLE_M503  // Saves ~2700 bytes of PROGMEM. Disable for release!
+  #define EEPROM_CHITCHAT // Print a report on M500. Please keep turned on.
 #endif
 
 //

Marlin/example_configurations/wt150/Configuration.h

 #define EEPROM_SETTINGS
 
 #if ENABLED(EEPROM_SETTINGS)
-  // To disable EEPROM Serial responses and decrease program space by ~1700 byte: comment this out:
-  #define EEPROM_CHITCHAT // Please keep turned on if you can.
+  //#define DISABLE_M503  // Saves ~2700 bytes of PROGMEM. Disable for release!
+  #define EEPROM_CHITCHAT // Print a report on M500. Please keep turned on.
 #endif
 
 //