The guy who posted the previous review was referring to the forever looping logo animation overlay that prevents you to even delete the 1 duplicate it finds (though you can do it manually via library)
https://github.com/cadeyrn/bookmarks-organizer/issues/48 since Aug 14

Or another one with a screenshot https://github.com/cadeyrn/bookmarks-organizer/issues/46 since Aug 7

The broken search sometimes does work sometimes won't finish , from what i understand there is a needed api that is not yet available (atleast on the stable ffx release)

This extension has potential when the 57 hits , looking foward to test it (no new update rip rating)

After installing the add-on, I restarted FF 52.3.0 (running Mac OS X 10.11.6). Then I chose "broken bookmarks" and the add-on found 140.063 (yes 140 thousands!) bookmarks. Then I clicked on "check bookmark" and after 5 minutes I saw 211 checked but after 20 minutes the number of items checked was still 211. No numbers in warmings and errors fields. The add on is still working because I see in the middle of the window 3 circles moving ... and I cannot have any feedback nor choose any other option (like "duplicates", for instance). I'm (sadly) going to remove the add on ...unless I can have any suggestion to have the add on working ... I can't ever rate this add on...maybe too much bookmarks?

- Restarted FF after installing.
- Opened the Firefox extension.
- Selected Broken Bookmarks.
- Selected Check Bookmarks...
- It scanned 4979 bookmarks.
- It identified 1453 warnings.
- It also identified 381 errors.

THEN NOTHING - (waited for 12 minutes)
The 'dot' progress indicator kept moving.


Selected Duplicates > Check Bookmarks.
Nothing !

Selected Missing Bookmark Names > Check Bookmarks.
Nothing !

Scan
From 5125 checked 5123 and after an hour I closed that link