5:00 You don't have to delete the hole sketch. Either select break all from the external reference dialogue, or just edit sketch, delete the relations, and reapply them. You also dont have to hide parts, many times in 3D view skerxhes are selectable, and usually solidworks prioritise sketches. You can also use selection filter to be able to only select sketches, so if no sketxhes are visible at part level, only assembly sketches will be used when creating relations.