Thank you. That's what we also figured out. It is just frustrating how Canvas lacks so severely even in the most basic functionality which shouldn't be a difficult thing to implement. We also figured out that if you set the quiz as an ungraded survey, then you still see who has completed/not completed it and it doesn't appear in the assignment section. However, it still appears under the "To do" column for students and there is also no way to disable or hide anything from students in the "To do" column on Canvas. So, indeed the only option is to publish it just before, which may be a menial task, but still takes up time.