I have Win 11 with current updates (KB4023057). and Start11 beta 1.12.1.
I had installed the Start11 beta 1.11.1 (I believe that was the beta, but all that info is gone now).
I wanted it because Win 11 does not allow ungrouping of items on the taskbar. That beta fixed that issue.
Also (and more important), it also fixed copy and paste between two apps that are on the taskbar which again Win 11 doesn't support (although this feature had been allowed for many years and releases).
I got the automatic update to 1.12 and guess what? The copy and paste feature is missing. I upgraded to 1.12.1 beta but C & P still doesn't work.
I cannot find any option to make this work (like the option to ungroup in Start11).
If anything, I would like to go back to beta 1.11.1 that worked, as I use this many times a week.
To explain this clearly, I have four apps opened on the taskbar. one is Xplorer2 and there are three other apps that I will C&P from there. Usually, one would highlite some copy items in Xplorer2 and drag them down to an icon app on the taskbar. That would make the app become active and full screen and then I could paste to it.