How can I delete the "Migrated Quizzes" assignment group?
So I migrated a quiz to New Quizzes but I ended up deleting the New Quiz. However, the "Migrated Quizzes" assignment group is still there, showing up on student grade reports, and I want to remove it. Yet, as you can see from the screenshot, I'm unable to delete the assignment group even though it has nothing in it because the Delete option is greyed out.
I just tried this in a test course (in production) and could not replicate your experience. The option to delete the "Migrated Quizzes" assignment group is available regardless of whether there is a quiz in the group or if it's empty, and didn't make a difference whether the assignment groups are weighted or not. (My role is Teacher in the test course, in case it makes a difference.)