Excellent addon for not only adding your own search engines to Firefox but also for backing up and importing them (whenever you move to a new PC or after a format). Thanks Dev!!

Tip: when exporting your search engines, it asks you to locate the "search.json.mozlz4" file.
This file can be found if you:
type Run in the Start Menu,
open the Run app,
then type %appdata% which opens your user folder,
then open Mozilla / Firefox / Profiles / xxxxxxxx.default-release
(xxxxxxxx will be a bunch of random numbers and letters)

I usually create a shortcut of that last folder and place it on my desktop, then hit Browse from this addon and double click the shortcut to get there. Easy peasy.