Excellent functionality, very useful - until it prevented the saving of bookmarks.
Disabling the extension restores normal bookmarking operation.
Linux, FF v64 and at least one version earlier.

Problem:
I bookmark a page, it's visible in the bookmarks list, but when restarting FF it's no longer there.
Also, after bookmarking one page on a tab and moving to the next (un-bookmarked) page on a different tab, that page shows as bookmarked: the star in the address bar is filled in blue - but this is bogus: clicking on it does nothing and neither does the menu entry "Bookmarks|Bookmark This Page".

Essentially I find the same problem as poster m4758406 (5 months ago at the time of this post).

A very poor workaround can be had by keeping an external list of sites, and then copy/pasting each URL one at a time. Bookmark one tab, close FF, restart (bookmark was saved) - then copy/paste bookmarking the next in the same way.

I'm not sure the developer is still actively supporting this and his other extensions: the last updates for them are showing as a year ago.
That's unfortunate. Aside from the bookmarking problem this extension was very useful.