Session Manager

Session Manager is a Firefox extension that enhances the web browser's functionality, by allowing you to save and manage multiple sessions. It can be easily installed and set up.
The extension integrates into the Firefox main menu, from where you can save the session or current window, rename, delete or group sessions, as well as open the sessions folder or clear the "Closed" list.
A wide range of settings can be configured from the Options screen. For example, you can establish the maximum number of remembered closed windows and tabs (per windows) for the undo function, as well as make the web browser always restore the list of reopenable closed windows and tabs for all windows.
In addition, you can modify the default saved sessions location, encrypt the saved session and closed window data, enable crash recovery mode and logging, as well as set Firefox to prompt for a session at startup and to automatically back up the current session at shutdown, among others. Settings can be exported to file for further use.
Session Manager barely uses CPU and system memory, so it doesn't hog the computer's resources. It has a good response time and works fine, without making the web browser hang, crash or pop up error dialogs. We haven't encountered any issues throughout our testing. To conclude, Session Manager adds a welcomed functionality to Firefox that surely pleases all types of users, especially experienced ones.