### 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 (!surface->has_focus() && (!get_viewport()->gui_get_focus_owner() || !get_viewport()->gui_get_focus_owner()->is_text_field())) {
		surface->grab_focus();
	}
}
void Node3DEditorViewport::_surface_mouse_exit() {
	_remove_preview_node();
	_reset_preview_material();
	_remove_preview_material();
}
void Node3DEditorViewport::_surface_focus_enter() {
	view_menu->set_disable_shortcuts(false);
}
void Node3DEditorViewport::_surface_focus_exit() {
	view_menu->set_disable_shortcuts(true);
}
bool Node3DEditorViewport ::_is_node_locked(const Node *p_node) {