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

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

See also:

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

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

• keep a backup copy of places.sqlite in case a new places.sqlite database has to be created
• http://kb.mozillazine.org/Unable_to_process_the_backup_file_-_Firefox

You can use the button on the "Help -> Troubleshooting Information" (about:support) page to go to the current Firefox profile folder or use the about:profiles page.

• Help -> Troubleshooting Information -> Profile Directory:
  Windows: Show Folder; Linux: Open Directory; Mac: Show in Finder
• http://kb.mozillazine.org/Profile_folder_-_Firefox

Thank you for your quick response, cor-el. I apologize for not responding sooner. I appreciate the add-on link, however, in the wake of WannaCry, the person I share the device with doesn't want me downloading any add-ons. I'll try your alternative suggestion.

Out of curiosity, will leaving the bookmarks as they are cause any problem?

Thanks again

Hi.

There is also a button on the "Help -> Troubleshooting Information" page (about:support) to check the integrity of the places.sqlite database that you can give a try. I don't know whether and in what way Places Maintenance is doing more.

I had a similar problem: The All Bookmarks folder was duplicated as a subfolder of one of my Bookmarks Menu folders. After deleting/rebuilding the places.sqlite file, I was allowed to do a simple deletion of the duplicate All Bookmarks folder. So far, no detected problems.