I was glad to find a replacement for another one, but I can’t make it work with some links… Don’t what I’m doing wrong. Also did not find how to manage the window.

Does not work on "faceitfinder"
We need the last word in the link for work. ~$*$~

Why did you stop remembering the changed settings? When it became difficult to say, I haven't changed anything for a long time, but after restarting the changes disappear.

Почему перестало запоминать измененные настройки? Когда это стало трудно сказать, давно ничего не менял, но после перезапуска изменения пропадают

There is no better at the moment, but In the latest versions of Firefox, no changes in this add-on are saved, I add new search engines, after rebooting the browser, they disappear, as well as setting up auto copy.

The addons works for the most part, but the reason I installed it was to use my bookmark searches for images and none of them work. The "%s" isn't replaced by the image URL, so I have to copy paste all my bookmarks into the addon :/

Looks nice, but why doesn't it use the opensearch plugins installed?

Impressive and very complete extension.
It allows me to synchronize all my global search engines using bookmarks. I also add custom local search engine depending on my need.
I don't know why this is not an extension with the Mozilla's "Featured Extension" badge (for instance "Swift Selection Search" has the badge, but is really less powerful).
One issue though:
When using bookmarks, the separators are taking the same height as a normal bookmark in the context search menu. Couldn't you display it like a object in the local Selection Context Search menu (reduced height)? I will review my rating to 5 stars is this issue is fixed.

Bonus points for customization of the text and of the folder name.

It doesn’t read the bookmarks in my case though, and I cannot debug this because of obfuscated source code.

At least my security concerns are lifted: I forgot that Mozilla Team reviews the code of extensions.