Developer reply by Oleksandr
Rated 3 out of 5 stars
November 2017
was great but does not work anymore with Firefox 57
WARNING:
do not upgrade Firefox to version 57 or this add-on (and many others) will not work anymore!
Unfortunately, WebExtensions (the new API for Firefox 57+) does not have the functionality for the correct operation of this addon in Firefox.
But you can install Firefox 52 ESR and enjoy work until June 2018
https://www.mozilla.org/en-US/firefox/organizations/faq/
To create your own collections, you must have a Mozilla Add-ons account.