Chrome has always had the capability of adding custom search engines. They are just not entangled with your bookmarks.
Firefox is actually going to remove this feature from bookmarks, and you'll have to create new engines from this page: about:preferences#search
This has nothing to do with search engines, it substitutes the argument from the search bar into the destination url. "wp XYZ" -> "https://en.wikipedia.org/wiki/XYZ"
It has everything to do the browser feature known as "custom search engines", which is a URL replacement capability that was never limited to actual search engines.
As I said before, Mozilla is going to merge your bookmark keywords with custom search engines: https://bugzilla.mozilla.org/show_bug.cgi?id=1650874
I switched to FF a few years back I really do like it better, but honestly even if it crashed every hour on the hour I'd still use it over chrome for uBO alone.