### 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 NavigationScheme nav_scheme = (NavigationScheme)EDITOR_GET("editors/3d/navigation/navigation_scheme").operator int();
	real_t zoom_speed = 1 / 80.0;
	if (p_event.is_valid() && nav_scheme == NAVIGATION_MAYA && p_event->is_shift_pressed()) {
		zoom_speed *= 10;
	}
	NavigationZoomStyle zoom_style = (NavigationZoomStyle)EDITOR_GET("editors/3d/navigation/zoom_style").operator int();
	if (zoom_style == NAVIGATION_ZOOM_HORIZONTAL) {
		if (p_relative.x > 0) {
			scale_cursor_distance(1 - p_relative.x * zoom_speed);
		} else if (p_relative.x < 0) {
			scale_cursor_distance(1.0 / (1 + p_relative.x * zoom_speed));
		}
	} else {
		if (p_relative.y > 0) {
			scale_cursor_distance(1 + p_relative.y * zoom_speed);
		} else if (p_relative.y < 0) {
			scale_cursor_distance(1.0 / (1 - p_relative.y * zoom_speed));
		}
	}
}
void Node3DEditorViewport::_nav_orbit(Ref<InputEventWithModifiers> p_event, const Vector2 &p_relative) {