I also find it highly annoying that you can't enter "updated" notes, after playing a specific hole. Once you hit "Return" from scoreboard, you're on to next hole. And you might have additional notes to add to existing one. But that is not possible.
A notebook is carried in my backpocket IRL - and I can update existing notes or make new ones about the hole - both before and after I make the stroke at current location.
Seems only natural to me, that it would also be the case for the IGN notebook.