### 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 TRANSFORM_TRANSLATE: {
			if (_edit.snap || spatial_editor->is_snap_enabled()) {
				p_motion.snap(Vector3(p_extra, p_extra, p_extra));
			}
			if (p_local) {
				return p_original_local.translated_local(p_motion);
			}
			return p_original.translated(p_motion);
		}
		case TRANSFORM_ROTATE: {
			Transform3D r;
			if (p_local) {
				Vector3 axis = p_original_local.basis.xform(p_motion);
				r.basis = Basis(axis.normalized(), p_extra) * p_original_local.basis;
				r.origin = p_original_local.origin;
			} else {
				Basis local = p_original.basis * p_original_local.basis.inverse();
				Vector3 axis = local.xform_inv(p_motion);
				r.basis = local * Basis(axis.normalized(), p_extra) * p_original_local.basis;
				r.origin = Basis(p_motion, p_extra).xform(p_original.origin - _edit.center) + _edit.center;
			}
			return r;
		}
		default: {
			ERR_FAIL_V_MSG(Transform3D(), "Invalid mode in '_compute_transform'");
		}
	}
}
void Node3DEditorViewport::_surface_mouse_enter() {