Preheat Menu shortcut option (#20350)

Marlin/Configuration_adv.h

     #endif
   #endif
 
+  // Insert a menu for preheating at the top level to allow for quick access
+  //#define PREHEAT_SHORTCUT_MENU_ITEM
+
 #endif // HAS_LCD_MENU
 
 #if HAS_DISPLAY

Marlin/src/inc/Conditionals_post.h

   #endif
 #endif
 
+#if !PREHEAT_COUNT
+  #undef PREHEAT_SHORTCUT_MENU_ITEM
+#endif
+
 /**
  * Up to 3 PWM fans
  */

Marlin/src/lcd/menu/menu_main.cpp

   void menu_spindle_laser();
 #endif
 
+#if ENABLED(PREHEAT_SHORTCUT_MENU_ITEM)
+  void menu_preheat_only();
+#endif
+
 #if HAS_MULTI_LANGUAGE
   void menu_language();
 #endif
       ACTION_ITEM(MSG_HOST_START_PRINT, host_action_start);
     #endif
 
+    #if ENABLED(PREHEAT_SHORTCUT_MENU_ITEM)
+      SUBMENU(MSG_PREHEAT_CUSTOM, menu_preheat_only);
+    #endif
+
     SUBMENU(MSG_MOTION, menu_motion);
   }
 

Marlin/src/lcd/menu/menu_temperature.cpp

 
   #if PREHEAT_COUNT
     //
-    // Preheat for Materials 1 to 5
+    // Preheat for all Materials
     //
     LOOP_L_N(m, PREHEAT_COUNT) {
       editable.int8 = m;
   END_MENU();
 }
 
+#if ENABLED(PREHEAT_SHORTCUT_MENU_ITEM)
+
+  void menu_preheat_only() {
+    START_MENU();
+    BACK_ITEM(MSG_MAIN);
+
+    LOOP_L_N(m, PREHEAT_COUNT) {
+      editable.int8 = m;
+      #if HOTENDS > 1 || HAS_HEATED_BED
+        SUBMENU_S(ui.get_preheat_label(m), MSG_PREHEAT_M, menu_preheat_m);
+      #else
+        ACTION_ITEM_S(ui.get_preheat_label(m), MSG_PREHEAT_M, do_preheat_end_m);
+      #endif
+    }
+
+    END_MENU();
+  }
+
+#endif
+
 #endif // HAS_LCD_MENU && HAS_TEMPERATURE