I would like to be able to edit quiz item feedback after students have submitted a quiz, and have that updated feedback show up for all students.
When I am grading a quiz, I frequently realize that multiple students have the same misunderstandings. And if I haven't anticipated this in advance, then there is no way to address that in the question feedback for students who have already taken it. (I don't allow anyone to view results or feedback until after the quiz end date, so I'd be doing this before anyone had a chance to view the preexisting feedback.)
Note: I don't have quizzes.next at my school, so I don't know if this applies to that or only to the old quiz tool.