[when I set] the bluetooth keyboard aside and will navigate through a document to correct a few things by hand
It seems the OP is not going for cmd-z b/c they are off-keyboard and on-screen at the moments in question.
I wonder what correcting things “by hand” comes to without any interaction with the keyboard. Maybe picking suggested typo corrections? So, the Undoing in question would be undoing moves like that, I guess.
Shortcuts bar sure seems like the right answer!