### 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)

const Vector2i center = get_size() / 2.0;
	const real_t radius = get_size().x / 2.0;
	if (focused_axis > -2 || orbiting_index != -1) {
		draw_circle(center, radius, Color(0.5, 0.5, 0.5, 0.25));
	}
	Vector<Axis2D> axis_to_draw;
	_get_sorted_axis(axis_to_draw);
	for (int i = 0; i < axis_to_draw.size(); ++i) {
		_draw_axis(axis_to_draw[i]);
	}
}
void ViewportRotationControl::_draw_axis(const Axis2D &p_axis) {