The undo button is Control+Z or in Mac it’s Command+Z .
I have several keyboard layout installed on my computer. namely Russian Arabic and German.
The problem arises when I switch to German . see in German-keyboard-layout the position of Y and Z Is switched which means only in German you have to press Control+Y (the one between the t and u keys) this is an inconsistency and confusing and annoying.
Does this also occur in other applications? I am not on my Mac right now and can’t check, but as far as I know there are two German keyboard layouts. Try the other one.