Following the update to FF57 I am missing its top functionality "close similar tabs". I don't want to lower rating of this (formerly) great addon for some FF-related "mess" however this update makes this addon useless for me. I hope the author's gonna get over the new FF addon policy quickly... EDIT 2020: In fact, lack of this functionality in general made me make my own extension. If interested, check out "Clean the mess!" https://addons.mozilla.org/en-US/firefox/addon/clean-the-mess/