When you have the local browser save / open window open you can right click on a file to rename, delete or download a file. Same also works on the cloud dialog.
So that gives you a way to back up files elsewhere without having to open the projects, and clean up to get some extra space. I might add an option in the future to allow you to copy files directly to a different "service", it would make moving files between dropbox, local storage, google drive and onedrive a lot easier. Folders are also on the road map, but not at the top of the priority list.