Rich gave you several suggestions that can do that sort of thing.
Sometimes it just requires thinking ahead a few steps. If I was modeling this piece and like you decided to add the hand hole late in the design, I would have put the hand hole in the left hand side component, then replaced the right side component with the left one (select the old right side, right click on the left one in the components panel and choose Replace Selected. Then Make Unique and use the shelf to cut a new dado in the new right side with Eneroth Trim or Bool Tools 2 Trim. It take a little forethought and planning for possible changes but it's not difficult and takes little time, especially with keyboard shortcuts.