You can undo and redo in Apple Notes, event the options are not visible all the time.
When it comes to undo your mistakes in Apple Notes, you may find it a bit confusing because there are no visible buttons at all times.
Nonetheless, there are a couple of ways to undo and redo in the Notes app of your iPhone.
One is tapping the Draw button from your keyboard’s button bar. When you enter drawing mode, you’ll see the undo/redo buttons on top of the screen.
The second option is to undo or redo by shake. If you shake your iPhone when using Apple Notes, you’ll be shown a menu that allows you to undo or redo, depending on the case.
It’s actually so much faster this way.