### 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)

Node3DEditorSelectedItem *se = selected ? editor_selection->get_node_editor_data<Node3DEditorSelectedItem>(selected) : nullptr;
	if (se) {
		return se->subgizmos.has(p_id);
	}
	return false;
}
bool Node3DEditor::is_current_selected_gizmo(const EditorNode3DGizmo *p_gizmo) {
	Node3DEditorSelectedItem *se = selected ? editor_selection->get_node_editor_data<Node3DEditorSelectedItem>(selected) : nullptr;
	if (se) {
		return se->gizmo == p_gizmo;
	}
	return false;
}
Vector<int> Node3DEditor::get_subgizmo_selection() {
	Node3DEditorSelectedItem *se = selected ? editor_selection->get_node_editor_data<Node3DEditorSelectedItem>(selected) : nullptr;
	Vector<int> ret;
	if (se) {
		for (const KeyValue<int, Transform3D> &E : se->subgizmos) {
			ret.push_back(E.key);
		}
	}
	return ret;
}
void Node3DEditor::add_control_to_menu_panel(Control *p_control) {