### 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)

right_panel_split->add_child(p_control);
	right_panel_split->move_child(p_control, 1);
}
void Node3DEditor::remove_control_from_left_panel(Control *p_control) {
	left_panel_split->remove_child(p_control);
}
void Node3DEditor::remove_control_from_right_panel(Control *p_control) {
	right_panel_split->remove_child(p_control);
}
void Node3DEditor::move_control_to_left_panel(Control *p_control) {
	ERR_FAIL_NULL(p_control);
	if (p_control->get_parent() == left_panel_split) {
		return;
	}
	ERR_FAIL_COND(p_control->get_parent() != right_panel_split);
	right_panel_split->remove_child(p_control);
	add_control_to_left_panel(p_control);
}
void Node3DEditor::move_control_to_right_panel(Control *p_control) {
	ERR_FAIL_NULL(p_control);
	if (p_control->get_parent() == right_panel_split) {
		return;
	}
	ERR_FAIL_COND(p_control->get_parent() != left_panel_split);
	left_panel_split->remove_child(p_control);
	add_control_to_right_panel(p_control);
}
void Node3DEditor::_request_gizmo(Object *p_obj) {