I can't figure out if sessions are tied to virtual desktops when they are saved and is it really important to me

Works well generally. I'm waiting for it to support tab groups!

Would be nice to be able to save Tab Groups also.

I've used this addon for many years and I honestly love it, but I found an issue that unfortunately I cannot overlook at work- it doesn't save history. If you don't need your history after closing the browser, then this is a 5-star addon. Previously, I gave it three stars because I couldn't use it at work, and rarely needed it at home. I updated it to four stars because I found a workaround. If you make sure every tab is loaded, and logged in, or gracefully logged out, and set it to not auto open the latest session, you can open every website, log in, then load your last session. Your tabs will load correctly, which usually means you don't need your history.

This is the explanation I previously wrote about my issues and the lower rating: The default Firefox session manager saves the history of every tab, which is incredibly important for me, but it also leaves me between a rock and a hard place. I have to use cloud software for work. It logs you out periodically. When you sign in, it will usually resume where you were; however, when you restart your browser, it resets the session, and after you log in, it lands you on the main page. If you have your tab history, you can navigate back to the page you were on; otherwise, you're stuck with 50 (to sometimes 200) useless tabs, and a mess trying to figure out what you were doing. On the other hand, the Firefox session manager can save only one session and is incredibly inconsistent; it's a coin flip whether it will work after a crash, and the only way to guarantee a session is saved is by killing Firefox from the task manager. If you sign out of your Windows account, restart, or your OS crashes, and you forget or are unable to kill Firefox from the task manager, you're completely screwed.

It seems to do most of what I expected. One part I had hoped is that it would remember window placement (where are they on screen ... and which virtual desktop are they on). Unfortunately, it doesn't do either. For me, this just seems to be another way to do what "Restore Session" already does.

Tab Session Manager has been a lifesaver, as Firefox's inbuilt Restore Session frequently doesn't restore all the tabs from the last session and puts tabs in wrong containers - TSM does this all perfectly. One annoyance - tabs restored with TSM seem to display the tab tooltip only once when hovering over a tab. There is no tooltip when hovering over the tab a second time. (I'm using Tree Style Tabs).
Update: discovered that tooltips always appear over over tabs that are in a container, but only once over tabs not in a container.

Nice but why is there nowhere in the settings stated (or a "switch-account") to which account I'm syncing? I can find out so it's not a huge problem, but it's also not a huge problem I think to just implement a mentioning somewhere in the settings ¯\_ (ツ)_/¯

Has stopped saving sessions automatically; must do so manually. Only sometimes registers when a window is closed and saves then.

EDIT: deleting any re-uploaded sessions seems to allow the extension to automatically save again.

I've been using Tab Session Manager by the developer sienori for years, and it has truly improved my browsing experience. This extension is incredibly user-friendly, offering a seamless way to save and restore browsing sessions with just a few clicks. Whether I'm working on a project, researching, or simply browsing for leisure, I can easily pick up right where I left off without worrying about losing any important tabs. The intuitive interface and reliable performance have made it an indispensable tool in my daily routine.

What sets Tab Session Manager apart is its versatility and thoughtful features. The ability to categorize and organize sessions, combined with the automatic backup functionality, ensures my sessions are always safe and accessible. It's highly customizable, allowing me to tailor it to my specific needs. As one of the Firefox Recommended Extensions, created by trustworthy developers, this extension meets the highest standards in security, functionality, and user experience. The developer sienori has done a fantastic job with regular updates and responsive support, making this extension a must-have for anyone looking to enhance their productivity and streamline their browsing habits. Highly recommended! 👍🏼

I've been using this add-on for years and I'm so happy with it , the only problem is that when I automatically loads the session at FF start , it opens a new window other than the one I already opened , I wonder if there is an option to make the saved sessions load in the same window I have already started

Is it possible to make an option to lock the extension so it requires a password to open your sessions?

BEWARE: the addon still seems to work OK for me, but since ~2021 improvements basically stopped and new changes are mostly to the list of donors. There's currently over 400 issues open in GitHub, and growing, with no answers. Cloud sync says it works, but not really. Time to start looking for alternatives.