I used to have a good experience with this addon and its older pre-FF57 incarnation, but these days it paralyses Firefox as soon as I install or enable it. Does it conflict with other addons or features e.g Firefox Containers? Firefox Sync?
running on KDE Neon (=Ubuntu)

Answering the developer: yes, I have hundreds of tabs open (most are suspended). That's probably the issue then, thanks for the advice. I'll move my rating from 2 to 4 stars as the addon itself is great.