### 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)

case VIEW_ALIGN_TRANSFORM_WITH_VIEW: {
			if (!get_selected_count()) {
				break;
			}
			Transform3D camera_transform = camera->get_global_transform();
			List<Node *> &selection = editor_selection->get_selected_node_list();
			undo_redo->create_action(TTR("Align Transform with View"));
			for (Node *E : selection) {
				Node3D *sp = Object::cast_to<Node3D>(E);
				if (!sp) {
					continue;
				}
				Node3DEditorSelectedItem *se = editor_selection->get_node_editor_data<Node3DEditorSelectedItem>(sp);
				if (!se) {
					continue;
				}
				Transform3D xform;
				if (orthogonal) {
					xform = sp->get_global_transform();
					xform.basis = Basis::from_euler(camera_transform.basis.get_euler());
				} else {
					xform = camera_transform;
					xform.scale_basis(sp->get_scale());
				}
				if (Object::cast_to<Decal>(E)) {
					/
					/
					/
					xform.basis.rotate_local(Vector3(1, 0, 0), Math_TAU * 0.25);
				}