There ist no cmd-Z in the scratchpad, what makes is less useable for drafting chunks of text that should not get lost (hitting on the wrong key after “highlight all” cost me quite a bit of work recently).
There was a thread on this, but it seems that the problem didn’t get resolved: https://forum.literatureandlatte.com/t/just-confirming-no-undo-in-scratchpad/27356/1
I still experience this problem with 2.8.1.2 on OSX 10.12.3. Any ideas how to remedy?
no reactions yet … dear developers, did I chose the right way to address this topic? Should I better write a support request by mail?
one last try to bring this to the attention of an admin or developer … strange, the responses here were always extremely quick! Maybe my fault somehow?
Usually no answer here means that the other forum users (like me) have never encountered the problem and so have no ideas to suggest. 
The actual Scrivener tech support people do scan the forums, but don’t always notice everything. I suggest you contact them directly:
literatureandlatte.com/support.php
has the info on how.
Hope this helps!