MacOS 10.14.6 (Mojave)
Logic Pro 10.4.8
I swear it used to work. For the past several weeks I've been noticing that Cmd-Z doesn't seem to work in the piano roll.
The most recent change I've made (a new note, a dragged not, deleted note, etc.) does not always show as the annotated action in File->Undo. (in fact, it usually shows some event I didn't even do — e.g. I just looked now and a freshly opened project where I've done nothing other than open up the piano roll on a region and it shows "Big Saw: detune" )
If I look in the File->Undo History… dialog I sometimes (usually?) see the event I want to undo, and I can click to the prior event and undo things.
But Cmd-Z doesn't ever work. I'm pretty sure it used to. I've peeked at the Key Commands editor and Cmd-Z is there (greyed out- presumably because it's a system wide binding?)