The worst add-on I had on my system for months. Had the same running in Chrome, where it works quite well. On Firefox (72.01, 64 bit) win7 64 pro, it let me lose more than 250 tabs collected over a long time. Hope to retrieve them in my backups, but this add-on should be taken of the list immediately. One star is still one too many.
If the developers want to keep a small fraction of credibility, they should publish a method how to retrieve the lost tabs yet today.