@waltx Goto the URL opera://about, take note of the "profile" path, close Opera, delete the "Bookmarks" and "BookmarksExtras" files. However, if you need to save your bookmarks, before you close Opera, goto the URL opera://bookmarks and use the drop-down at the bottom left to export your bookmarks as an html file. Then, after you delete the bookmark files in the profile folder (while Opera is closed), start Opera back up, and everything is fine, you can go back to opera://bookmarks and use the drop-down to import the HTML to get your bookmarks back. Once they're back, on the opera://bookmarks page, you can move them into the folders you want and delete and empty folders that remain.
If you use Opera Sync though and sync bookmarks, you might want to sign out of Opera Sync before you close Opera to delete the bookmark files. Then, in addition to deleting the bookmark files, delete the sync folder in the profile folder. Then, once everything is working correctly and you sign back into Opera Sync, if the probably happens again, you'll know it's an issue with your Opera Sync data and you'll have to reset it at https://sync.opera.com/ to fix it, and then repeat the deleting of the bookmark files and sync folder, and then import your HTML file and sign into sync again.
If that doesn't fix it, you could uninstall Opera (don't use to delete your data when uninstalling) and reinstall Opera to repair Opera's program files to see if that helps.
If that doesn't fix it, while Opera is closed, you can rename the profile folder so that when Opera starts up, it creates fresh profile. You'll lose your settings and data this way though.
