This Add-On Might Work, BUT . . .

So, first I encourage everyone to read the "About this extension" section before using the extension to familiarize yourself with a few things like it's Features, Shortcuts and Planned features. Now, the 'Bookmarks Organizer' does what it claims. However, there are some things that the developer didn't think of. One of them and maybe the most important, is a Pause and/or Stop button. Having a Pause and/or Stop Button would be helpful for anyone that has 5000 - 10000+ bookmarks, for the following reasons; It would allow anyone using this extension to pause it and/or stop it, so they could go through the bookmarks that have already been scanned. The other reason is that, if you expect this scan to only take 10 to 25 minutes, think again, especially if your a bookmark addict and you have 5000 - 10000+ bookmarks saved. Because with that many bookmarks saved it's going to take a ... a few hours if not more.
The only other thing I can think of is something that apparently will be added to an up and coming version of the extension. That the ability or the option to 'select multiple bookmarks at once rather than only being able to delete them one by one'. Other than that, give this extension a try, it does work. It's a little slow, but it works. I gave it 3 Stars, but I would have given it 5 stars if it wasn't so slow.