### 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)

if (p_state.has("auto_orthogonal")) {
		auto_orthogonal = p_state["auto_orthogonal"];
		_update_name();
	}
	if (p_state.has("auto_orthogonal_enabled")) {
		bool enabled = p_state["auto_orthogonal_enabled"];
		view_menu->get_popup()->set_item_checked(view_menu->get_popup()->get_item_index(VIEW_AUTO_ORTHOGONAL), enabled);
	}
	if (p_state.has("display_mode")) {
		int display = p_state["display_mode"];
		int idx = view_menu->get_popup()->get_item_index(display);
		if (idx != -1 && !view_menu->get_popup()->is_item_checked(idx)) {
			_menu_option(display);
		} else {
			idx = display_submenu->get_item_index(display);
			if (idx != -1 && !display_submenu->is_item_checked(idx)) {
				_menu_option(display);
			}
		}
	}
	if (p_state.has("lock_rotation")) {
		_set_lock_view_rotation(p_state["lock_rotation"]);
	}
	if (p_state.has("use_environment")) {
		bool env = p_state["use_environment"];
		if (env != camera->get_environment().is_valid()) {
			_menu_option(VIEW_ENVIRONMENT);
		}
	}
	if (p_state.has("listener")) {