Ever since Firefox 63 was released, this addon causes Firefox to become unresponsive with a huge memory leak when opening a large amount of tabs from a session restore. In most cases, the memory leak is so severe that my system starts swapping non-stop even though i have 4GB or RAM and the firefox process needs to be killed in order to get my computer to respond properly again.

Apparently, there was a change in the way Firefox opens tabs on startup with a new "discarded" property for lazy loading which causes issues with most addons dealing with tabs that havent been updated yet.

A workaround for this issue is to temporarily disable this addon before clicking on the button to restore tabs and to turn it back on once the tabs are loaded.

Other than that, this addon works great in sorting multiple tabs and closing duplicate tabs opened in error. I have no problem updating my review once this addon is updated to work with Firefox 63 or higher.