Acerca deste extra
You may unable to restore multiple tabs because the user pref browser.sessionstore.max_tabs_undo is 1 by default. If you need to restore more tabs, you have to change the pref value bigger according to your preference.
Para criar as suas próprias coleções, tem de ter uma conta dos extras da Mozilla.
Some add-ons ask for permission to perform certain functions. Since you’re in control of your Firefox, the choice to grant or deny these requests is yours.
Please note this add-on uses legacy technology, which gives it access to all browser functions and data without requesting your permission.