Sanity check USER_GCODE formatting

Marlin/src/inc/SanityCheck.h

@@ -2024,6 +2024,29 @@ static_assert(sanity_arr_3[0] > 0 && sanity_arr_3[1] > 0 && sanity_arr_3[2] > 0
   #error "GCODE_MACROS_SLOTS must be a number from 1 to 10."
 #endif
 
+#if ENABLED(CUSTOM_USER_MENUS)
+  #ifdef USER_GCODE_1
+    constexpr char _chr1 = USER_GCODE_1[strlen(USER_GCODE_1) - 1];
+    static_assert(_chr1 != '\n' && _chr1 != '\r', "USER_GCODE_1 cannot have a newline at the end. Please remove it.");
+  #endif
+  #ifdef USER_GCODE_2
+    constexpr char _chr2 = USER_GCODE_2[strlen(USER_GCODE_2) - 1];
+    static_assert(_chr2 != '\n' && _chr2 != '\r', "USER_GCODE_2 cannot have a newline at the end. Please remove it.");
+  #endif
+  #ifdef USER_GCODE_3
+    constexpr char _chr3 = USER_GCODE_3[strlen(USER_GCODE_3) - 1];
+    static_assert(_chr3 != '\n' && _chr3 != '\r', "USER_GCODE_3 cannot have a newline at the end. Please remove it.");
+  #endif
+  #ifdef USER_GCODE_4
+    constexpr char _chr4 = USER_GCODE_4[strlen(USER_GCODE_4) - 1];
+    static_assert(_chr4 != '\n' && _chr4 != '\r', "USER_GCODE_4 cannot have a newline at the end. Please remove it.");
+  #endif
+  #ifdef USER_GCODE_5
+    constexpr char _chr5 = USER_GCODE_5[strlen(USER_GCODE_5) - 1];
+    static_assert(_chr5 != '\n' && _chr5 != '\r', "USER_GCODE_5 cannot have a newline at the end. Please remove it.");
+  #endif
+#endif
+
 #if ENABLED(BACKLASH_COMPENSATION) && IS_CORE
   #error "BACKLASH_COMPENSATION is incompatible with CORE kinematics."
 #endif