Add HAS_HOTEND_OFFSET_Z conditional

Marlin/src/gcode/config/M218.cpp

     report = false;
   }
 
-  #if ENABLED(DUAL_X_CARRIAGE) || ENABLED(SWITCHING_NOZZLE) || ENABLED(PARKING_EXTRUDER)
+  #if HAS_HOTEND_OFFSET_Z
     if (parser.seenval('Z')) {
       hotend_offset[Z_AXIS][target_extruder] = parser.value_linear_units();
       report = false;
       SERIAL_ECHO(hotend_offset[X_AXIS][e]);
       SERIAL_CHAR(',');
       SERIAL_ECHO(hotend_offset[Y_AXIS][e]);
-      #if ENABLED(DUAL_X_CARRIAGE) || ENABLED(SWITCHING_NOZZLE) || ENABLED(PARKING_EXTRUDER)
+      #if HAS_HOTEND_OFFSET_Z
         SERIAL_CHAR(',');
         SERIAL_ECHO(hotend_offset[Z_AXIS][e]);
       #endif

Marlin/src/inc/Conditionals_LCD.h

   #undef HOTEND_OFFSET_Y
 #else                                                         // Two hotends
   #define HOTENDS       EXTRUDERS
-  #if ENABLED(SWITCHING_NOZZLE) && !defined(HOTEND_OFFSET_Z)
-    #define HOTEND_OFFSET_Z { 0 }
-  #endif
 #endif
 
 #define HOTEND_LOOP() for (int8_t e = 0; e < HOTENDS; e++)

Marlin/src/inc/Conditionals_post.h

 /**
  * Default hotend offsets, if not defined
  */
+#define HAS_HOTEND_OFFSET_Z (HOTENDS > 1 && (ENABLED(DUAL_X_CARRIAGE) || ENABLED(SWITCHING_NOZZLE) || ENABLED(PARKING_EXTRUDER)))
 #if HOTENDS > 1
   #ifndef HOTEND_OFFSET_X
     #define HOTEND_OFFSET_X { 0 } // X offsets for each extruder
   #ifndef HOTEND_OFFSET_Y
     #define HOTEND_OFFSET_Y { 0 } // Y offsets for each extruder
   #endif
-  #if !defined(HOTEND_OFFSET_Z) && (ENABLED(DUAL_X_CARRIAGE) || ENABLED(SWITCHING_NOZZLE))
+  #if HAS_HOTEND_OFFSET_Z && !defined(HOTEND_OFFSET_Z)
     #define HOTEND_OFFSET_Z { 0 }
   #endif
 #endif

Marlin/src/module/configuration_store.cpp

         SERIAL_ECHOPAIR_P(port, "  M218 T", (int)e);
         SERIAL_ECHOPAIR_P(port, " X", LINEAR_UNIT(hotend_offset[X_AXIS][e]));
         SERIAL_ECHOPAIR_P(port, " Y", LINEAR_UNIT(hotend_offset[Y_AXIS][e]));
-        #if ENABLED(DUAL_X_CARRIAGE) || ENABLED(SWITCHING_NOZZLE) || ENABLED(PARKING_EXTRUDER)
+        #if HAS_HOTEND_OFFSET_Z
           SERIAL_ECHOPAIR_P(port, " Z", LINEAR_UNIT(hotend_offset[Z_AXIS][e]));
         #endif
         SERIAL_EOL_P(port);