Rated 5 out of 5 stars

This addon is the only reason I am not updating Firefox to version 57. Also I am switching to Waterfox 56. Some info:

https://www.reddit.com/r/firefox/comments/6lcq7r/session_manager_dev_says_session_manager/
https://www.reddit.com/r/firefox/comments/7gqv65/apis_needed_for_session_manager_to_become/
https://www.reddit.com/r/firefox/comments/7dxmu4/why_firefox_had_to_kill_your_favorite_extension/dqsbz0u/
https://www.reddit.com/r/firefox/comments/7hyf2w/session_management_in_firefox_quantum/
https://www.mozdev.org/bugs/show_bug.cgi?id=26384
http://forums.mozillazine.org/viewtopic.php?f=48&t=2308889

PLEASE, VOTE FOR APIs NEEDED BY SESSION MANAGER:
https://www.reddit.com/r/firefox/comments/7m8nvx/can_session_manager_tab_session_manager_coexist/drslt43/

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