I sometimes use ungraded Essay questions in Quizzes for students to submit explanations or ideas for the course. It works well because they will consistently do the graded quizzes, and will provide an answer to the ungraded Essay questions if they are there. They are far less likely to complete the ungraded Essay question if it is in a separate task.
The problem, however, is that Canvas insists that I then need to manually grade *every single quiz* even though the essay question is worth 0. This makes no sense. I can understand providing instructors with the option of giving extra credit here. But that could just as easily be achieved by automatically setting 0 as the default grade for every question that is worth 0.