Rated 5 out of 5 stars

Five gold stars.

Session Manager is – amongst many other things – an essential workaround for a Mozilla bug that can cause the first window of Firefox to be non-functional for a variety of extensions.

https://bugzilla.mozilla.org/show_bug.cgi?id=1378459#c34

Long live legacy Session Manager! Long live Firefox 56!

My top ten extensions for Firefox 56.0.2:

https://addons.mozilla.org/collections/grahamperrin/t10/

This review is for a previous version of the add-on (0.8.1.13).