It is not really slow if you think about it how the Bookmarks Organzier works. While I could make a few changes to make it a bit (not a lot!) faster if would mean that the quality of the results could no longer be the same. From a quality POV the Bookmarks Organizer has the most advanced algorithm to determine if bookmarks are still valid or not. We talk about bookmarks. I think false results are really bad for bookmarks. That's why I used an quality-focused approach.

Giving only one star just because it hasn't all the features you would like to see is a very bad way to interact with an add-on developer. There are no surprises at all, I described in detail what this add-on offers. So if it's not enough you could could know it before you installed the add-on. One star makes sense if the add-on does not hold what it promised but that's really nothing you could say about this add-on.

FWIW, I accept pull requests for enhancements and new features.