aren't workspaces the same as containers? when I right click the new tab icon in firefox it gives me an option to open them in work, personal, banking, etc or to create a new container
3 is also built in, called firefox sync. You can open any tab from any device on another one and send tab(s) to other devices
For the containers vs. workspaces - I was sloppy with the term, what I meant is different "views" which include sets of tabs. One slight difference is that containers give you a clean slate for each (as in, if you're logged in to a site in container one, you need to re-login in container 2). In any case, it's a good enough solution for me, thanks for the heads up!
"opening any tab on another device" is not what I'm looking for, though - I want to restore entire wokspaces/tab groups/containers across instances, not one by one, then arrange them again into containers.
Sometimes I really wish that firefox sync was a bit smarter. The sorting seems so random sometimes and there is no grouping per window or anything. So when looking to open a tab when the computer has 5 windows with ~5-20 tabs per window open and they appear in a random order it can get very frustrating.
Also sometimes when sending specific tabs to my tablet or phone on android there is no notification, even if the app is open. Then I have to open the sync settings and manually press "Sync now" to trigger the notifications.
3 is also built in, called firefox sync. You can open any tab from any device on another one and send tab(s) to other devices