Restore session is gone. It was at the upper left corner
There is no such option anymore in Firefox. You can find restore function in our another addon Live Start Page:
Chrome: https://chrome.google.com/webstore/detail/live-start-page-living-wa/ocggccaacacpienfcgmgcihoombokbbj?hl=en
Firefox: https://addons.mozilla.org/en-US/firefox/addon/live-start-page-lst/
Customer support service by UserEcho
Ideas
There is no such option anymore in Firefox. You can find restore function in our another addon Live Start Page:
Chrome: https://chrome.google.com/webstore/detail/live-start-page-living-wa/ocggccaacacpienfcgmgcihoombokbbj?hl=en
Firefox: https://addons.mozilla.org/en-US/firefox/addon/live-start-page-lst/