10-10-24: still good not perfect but pretty good.
aug, 2024: it's gotten much better. Recommended
Sept 2022: It's gotten better but the thing that remains that is really annoying is that it won't load the saved urls automatically and you have to disable and re-enable it to get the saved urls to load. The problem with the auto opening of the tabs has been resolved in their settings, so that is not an issue now. But I am sick and tired of having to disable and re-enable it to get it to load on command. I dont' want AUTO load but I do want them to load when I issue the command.

June, 2022: It's gotten better, easier to use. On some browsers such as epic, it will not auto activate and you have to disable and reenable to get it to show. Need a better way to save the tabs when it goes haywire. Should have an auto setting to automatically lock the tabs.
Nov 10, 2021:
Demoted this add on to ONE STAR.
It acts like trojan or malware and opens a second FFOX window without user input and with setting set to open tab only, ignores the setting and opens a new window. Reported as malware.
mostly disabled it. Breaks Loads whether you ask it to or not and then breaks your vpn or music connection in doing so. Seems pretty obvious they are messing with your other browsing connections. It's only good for one thing, that is if you have to open many URLS and don't want to bother pressing the keys to make a book mark. I consider this spyware. Don't know why mozilla recommends it, but they must have low standards.