### Godot version

Master (4.2)

### System information

Windows 11 - Vulkan - Nvidia RTX 4070 - intel i5 13600KF

### Issue description

As you can see in the video when you try to add multiple scenes in to the 3D viewport (only with multiple scenes) the editor throws this error.

```
ERROR: Can't add child '@Node3D@18837' to '@SubViewport@9274', already has a parent '@SubViewport@9274'.
   at: (scene\main\node.cpp:1411)
```


Video: https://youtu.be/BVcCIigQJDw

This happens in the latest master (pulled on 2.11.2023).

### Steps to reproduce

Drag couple of the 3d mesh scenes into the 3D viewport and then select multiple scenes and drag them over and observer the error.

### Minimal reproduction project

[TestSceneDragAndDrop.zip](https://github.com/godotengine/godot/files/13253741/TestSceneDragAndDrop.zip)

case NOTIFICATION_EXIT_TREE: {
			_finish_indicators();
		} break;
		case NOTIFICATION_THEME_CHANGED: {
			_update_theme();
			_update_gizmos_menu_theme();
			sun_title->add_theme_font_override("font", get_theme_font(SNAME("title_font"), SNAME("Window")));
			environ_title->add_theme_font_override("font", get_theme_font(SNAME("title_font"), SNAME("Window")));
		} break;
		case EditorSettings::NOTIFICATION_EDITOR_SETTINGS_CHANGED: {
			/
			_finish_grid();
			_init_grid();
		} break;
		case NOTIFICATION_VISIBILITY_CHANGED: {
			if (!is_visible() && tool_option_button[TOOL_OPT_OVERRIDE_CAMERA]->is_pressed()) {
				EditorDebuggerNode *debugger = EditorDebuggerNode::get_singleton();
				debugger->set_camera_override(EditorDebuggerNode::OVERRIDE_NONE);
				tool_option_button[TOOL_OPT_OVERRIDE_CAMERA]->set_pressed(false);
			}
		} break;
		case NOTIFICATION_PHYSICS_PROCESS: {
			if (do_snap_selected_nodes_to_floor) {
				_snap_selected_nodes_to_floor();
				do_snap_selected_nodes_to_floor = false;
			}
		}
	}
}
bool Node3DEditor::is_subgizmo_selected(int p_id) {