Rated 5 out of 5 stars

This is how you reenable Session Manager after it has been disabled by firefox 57:
Optional: Backup user profile, by copying the folder on hamburger menu-> '?'-> 'Troubleshooting Information'-> 'Open Folder'-> go up one level and copy the folder with random letters and numbers.
1. Install a version of firefox that supports "legacy" extensions, like FF ESR 52.
2. Run the browser. If Session Manager is still disabled, go to this page, Click "Add to Firefox" and install Session manager

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

Rated 5 out of 5 stars

Works surprisingly well (I'm surprised each time at the amount of thought put into the small details). Never encountered a bug or glitch. The interface is intuitive and works well for me.

It has more functions than I need, but most importantly, it saves browsing sessions with their history (meaning- it remembers the state of the windows/tabs so that the forward/back button is still active when they are reloaded).This way, it makes browsing more organized and helps me focus on the task at hand, as I can save other windows for later, instead of having them clutter the workspace and constantly distract me.

This review is for a previous version of the add-on (0.7.9.5.1-signed).