Can't add new search pages anymore

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.

An sich ein Tolles Tool - ABER: Bringt meinen FF61 ständig zum abstürzen und zertstört den Cut&Paste Buffer (extrem nervig). Support gibt's auch keinen - im Normalfall deaktivieren.

I've been trying to use this addon, by trying every version that is released, but after a few minutes that I enable this addon, I get a huge spike on Firefox memory usage till it uses all my memory available (I have 16GB RAM) and crashes my Firefox or sometimes leaves my window freezed!!! Can you please fix this?!? I'm certain that it's due to your addon because when I left it disabled I don't have this

Cannot Save, Please Update it!