I have found the "message students who..." function in gradebook very effective to nudging students to complete assignments. I suggest an option that, when you create the assignment, you can automatically choose to have the message sent to students after the turn in deadline has passed. I compare it to a "out of office" email that you might send to your colleagues. This personalized message will allow teachers to effectively use the message system and encourage student completion of work in a timely manner, without additional messages from the teacher.
Added to Theme
Improved UI Controls and Usability - Added or clearer CTAs and functionality Theme Status: Identified