It's definitely a frustrating experience to have to re-assign all of your containers if you happen to reinstall the browser. This should be easily supported by Firefox Sync.
Or if you happen to run Firefox between multiple devices. It's been a pain maintaining a couple of instances' synced when it comes to containers (again, such a shame).
There's an open issue [1], but no resolution yet as it seems.
Sorry about the bad news but sync dev is completely dead. Mozilla is scared of touching that code base. So don't expect any improvements or additions there .
Page shot is fantastic btw. No nonsense clipping in Linux (I use onenote on Windows and would love if shots could be exported outside as easily as they are created)
Once you enable testpilot, you can see the experiments. I think the page opens by itself after enabling. Select page shot and click a couple of buttons on different screens.