### 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)

Ref<Resource> res = ResourceLoader::load(path);
	ERR_FAIL_COND_V(res.is_null(), false);
	Ref<PackedScene> scene = Ref<PackedScene>(Object::cast_to<PackedScene>(*res));
	Ref<Mesh> mesh = Ref<Mesh>(Object::cast_to<Mesh>(*res));
	Node *instantiated_scene = nullptr;
	if (mesh != nullptr || scene != nullptr) {
		if (mesh != nullptr) {
			MeshInstance3D *mesh_instance = memnew(MeshInstance3D);
			mesh_instance->set_mesh(mesh);
			/
			String name = path.get_file().get_basename();
			mesh_instance->set_name(Node::adjust_name_casing(name));
			instantiated_scene = mesh_instance;
		} else {
			if (!scene.is_valid()) { /
				return false;
			} else {
				instantiated_scene = scene->instantiate(PackedScene::GEN_EDIT_STATE_INSTANCE);
			}
		}
	}
	if (instantiated_scene == nullptr) {
		return false;
	}
	if (!EditorNode::get_singleton()->get_edited_scene()->get_scene_file_path().is_empty()) { /
		if (_cyclical_dependency_exists(EditorNode::get_singleton()->get_edited_scene()->get_scene_file_path(), instantiated_scene)) {