Developer reply by Peter Leugner
Rated 5 out of 5 stars
I am a Linux user and used xclear for several years. I really miss it now. Is there really no chance to migrate it? Thanks anyway for the past years!
=== update
In lack of a better option, I filed a feature request at http://input.mozilla.com/ .
This addon uses XBL which is not supported anymore, the new WebExtensions don't support changing stuff outside a webpage, like the URL or search bar, so I can't upgrade unfortunately. Sorry!
To create your own collections, you must have a Mozilla Add-ons account.