a way to tell it when a doc is done and won’t be edited anymore
LO is intended to create documents. Not using them any more is a user decision and LO has nothing to do with it (and even must not interfere with user decisions). Use the OS file browser to delete your old outdated documents. Note that this will not remove them from the recent files list. The recent files list is just some log that LO internally maintains but this does not mean at all that the listed files still exist. They may have been removed unbeknownst to LO (e.g. in the file browser).