### 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 axis_is_orthogonal = ABS(plane.normal.dot(global_axis)) < orthogonal_threshold;
			double angle = 0.0f;
			if (axis_is_orthogonal) {
				_edit.show_rotation_line = false;
				Vector3 projection_axis = plane.normal.cross(global_axis);
				Vector3 delta = intersection - click;
				float projection = delta.dot(projection_axis);
				angle = (projection * (Math_PI / 2.0f)) / (gizmo_scale * GIZMO_CIRCLE_SIZE);
			} else {
				_edit.show_rotation_line = true;
				Vector3 click_axis = (click - _edit.center).normalized();
				Vector3 current_axis = (intersection - _edit.center).normalized();
				angle = click_axis.signed_angle_to(current_axis, global_axis);
			}
			if (_edit.snap || spatial_editor->is_snap_enabled()) {
				snap = spatial_editor->get_rotate_snap();
			}
			angle = Math::snapped(Math::rad_to_deg(angle), snap);
			set_message(vformat(TTR("Rotating %s degrees."), String::num(angle, snap_step_decimals)));
			angle = Math::deg_to_rad(angle);
			bool local_coords = (spatial_editor->are_local_coords_enabled() && _edit.plane != TRANSFORM_VIEW); /
			Vector3 compute_axis = local_coords ? local_axis : global_axis;
			apply_transform(compute_axis, angle);
		} break;
		default: {
		}
	}
}
void Node3DEditorViewport::update_transform_numeric() {
	Vector3 motion;