### 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)

Node3D *sp = Object::cast_to<Node3D>(p_obj);
	if (!sp) {
		return;
	}
	bool is_selected = (sp == selected);
	Node *edited_scene = EditorNode::get_singleton()->get_edited_scene();
	if (edited_scene && (sp == edited_scene || (sp->get_owner() && edited_scene->is_ancestor_of(sp)))) {
		for (int i = 0; i < gizmo_plugins_by_priority.size(); ++i) {
			Ref<EditorNode3DGizmo> seg = gizmo_plugins_by_priority.write[i]->get_gizmo(sp);
			if (seg.is_valid()) {
				sp->add_gizmo(seg);
				if (is_selected != seg->is_selected()) {
					seg->set_selected(is_selected);
				}
			}
		}
		if (!sp->get_gizmos().is_empty()) {
			sp->update_gizmos();
		}
	}
}
void Node3DEditor::_request_gizmo_for_id(ObjectID p_id) {