### 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)

bool all_locked = true;
	bool all_grouped = true;
	List<Node *> &selection = editor_selection->get_selected_node_list();
	if (selection.is_empty()) {
		all_locked = false;
		all_grouped = false;
	} else {
		for (Node *E : selection) {
			if (Object::cast_to<Node3D>(E) && !Object::cast_to<Node3D>(E)->has_meta("_edit_lock_")) {
				all_locked = false;
				break;
			}
		}
		for (Node *E : selection) {
			if (Object::cast_to<Node3D>(E) && !Object::cast_to<Node3D>(E)->has_meta("_edit_group_")) {
				all_grouped = false;
				break;
			}
		}
	}
	tool_button[TOOL_LOCK_SELECTED]->set_visible(!all_locked);
	tool_button[TOOL_LOCK_SELECTED]->set_disabled(selection.is_empty());
	tool_button[TOOL_UNLOCK_SELECTED]->set_visible(all_locked);
	tool_button[TOOL_GROUP_SELECTED]->set_visible(!all_grouped);
	tool_button[TOOL_GROUP_SELECTED]->set_disabled(selection.is_empty());
	tool_button[TOOL_UNGROUP_SELECTED]->set_visible(all_grouped);
}
template <typename T>
HashSet<T *> _get_child_nodes(Node *parent_node) {