The page where the quiz is edited and questions are assembled should not be narrow, otherwise the elements are too pressed together. I propose to remove the limitedwidth body class and to classify this as a bug.
(Up to Moodle 4.0 it was wide.)

FULL STEPS to reproduce
In a quiz activity go to the "Questions" in the secondary navigation.

WHAT YOU EXPECTED
You can edit the quiz comfortably.

WHAT ACTUALLY HAPPENS
You can not edit the quiz comfortably because the site is too narrow.