I had an instructor in a course where we use separate groups lose the submission files column. After some careful looking, it turned out that she had clicked the minus sign under "Submission Files" and collapsed the column. To my surprise, that turned out to affect all the assignments in that course. To my further surprise, it collapsed that column for all courses where she is a teacher.
My question is why such a local action has such far-reaching effect? What's the logic here?
I tried to read the fine manual on this question, but I fear I don't know the appropriate terms to search for, and this issue doesn't appear to be addressed in the assignment documentation.