I'm not quite sure if this has been suggested, but is there an Empty Folder(s) option? If there isn't, does anyone else think we should have one? Because my PM storage thing is at 61%, and deleting everything would take forever.
I've never seen anyone suggest it and I honestly don't think it's a half bad one. Not sure how easy that will be to tweak, so here's to hoping. In the mean time, the best you can do is delete per page by selecting all.