### 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)

preview_material_label->hide();
	preview_material_label_desc->hide();
	spatial_editor->set_preview_material(Ref<Material>());
	spatial_editor->set_preview_reset_material(Ref<Material>());
	spatial_editor->set_preview_material_target(ObjectID());
	spatial_editor->set_preview_material_surface(-1);
}
bool Node3DEditorViewport::_cyclical_dependency_exists(const String &p_target_scene_path, Node *p_desired_node) {
	if (p_desired_node->get_scene_file_path() == p_target_scene_path) {
		return true;
	}
	int childCount = p_desired_node->get_child_count();
	for (int i = 0; i < childCount; i++) {
		Node *child = p_desired_node->get_child(i);
		if (_cyclical_dependency_exists(p_target_scene_path, child)) {
			return true;
		}
	}
	return false;
}
bool Node3DEditorViewport::_create_instance(Node *parent, String &path, const Point2 &p_point) {