If they are all identical, then Firefox is preventing the deletion since all would appear to be the essential bookmark folders of your profile.

Can you use the automatic backups to roll back the situation? Instructions here: https://support.mozilla.org/en-US/kb/restore-bookmarks-from-backup-or-move-them. You should manually back up the current set of bookmarks, even if they're messed up, in case the backup is not what you want and you can't restore the new state automatically.

If the rollback fails, you could try manually editing the bookmark files, but let's not resort to that yet, as it is risky and lengthy to explain.

You can check for problems with the places.sqlite database file (bookmarks, history) in the Firefox profile folder.

• Places Maintenance: https://addons.mozilla.org/firefox/addon/places-maintenance/

If the Places Maintenance extension can't repair the places.sqlite database file then remove all places.sqlite file(s) in the Firefox profile folder to make Firefox rebuild the places.sqlite database file from the most recent JSON backup in the bookmarkbackups folder.

• http://kb.mozillazine.org/Bookmarks_history_and_toolbar_buttons_not_working_-_Firefox
• https://support.mozilla.org/kb/Bookmarks+not+saved#w_fix-the-bookmarks-file

Thank you both so much for your quick wisdom. I'll implement these steps when time permits.