For formative quizzes, I (and many other instructors in my department) have built quizzes with many "questions" where each "question" is taken at random from a set of questions in a question bank. That way as students take additional trials they are challenged by different questions. Quizzes currently allows us to select a subset of questions that are from the same question bank to populate a random question group in the quiz. Given the flat nature of the question banks (and item banks), this has allowed us to use a smaller number of question banks (still larger, more frustrating, and less efficient than if we could nest the banks, btw). This has also allowed us to remove and add questions easily from quizzes depending on exactly what topics need to be reinforced. Since, in some semesters, we do not cover specific examples and would like to not use those questions in the quiz.
Thus, to migrate to Quizzes.Next, one of the functionalities that we would want to see implemented is the ability to select a subset of items from an item bank to add to a quiz. This idea is based off of a question I posted to the quizzes.next guide How do I add all items or a random set from an item bank to an assessment in New Quizzes?