Developer reply by Oleksandr
Rated 5 out of 5 stars
doesn't work on new firefox ;/
Unfortunately, WebExtensions (the new API for Firefox 57+) does not have the functionality for the correct operation of this addon in Firefox 57+.
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.