### 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)

sel = selected_tmp;
				}
				item = item->get_parent();
			}
			item = sel;
		}
		if (_is_node_locked(item)) {
			continue;
		}
		Vector<Ref<Node3DGizmo>> gizmos = sp->get_gizmos();
		for (int j = 0; j < gizmos.size(); j++) {
			Ref<EditorNode3DGizmo> seg = gizmos[j];
			if (!seg.is_valid()) {
				continue;
			}
			if (seg->intersect_frustum(camera, frustum)) {
				selected.push_back(item);
			}
		}
	}
	for (int i = 0; i < selected.size(); i++) {
		if (!editor_selection->is_selected(selected[i])) {
			editor_selection->add_node(selected[i]);
		}
	}
	if (editor_selection->get_selected_node_list().size() == 1) {
		EditorNode::get_singleton()->edit_node(editor_selection->get_selected_node_list()[0]);
	}
}
void Node3DEditorViewport::_update_name() {