A couple weeks ago I covered Google Scripts in the classroom as my topic of the week. I also did a workshop on it last Friday during the high school's professional development day. Recording the webinar of it finally reached the top of my lengthy to do list, so here it is. Because I used Screencast-o-matic to record it and couldn't see the time I had taken, it stopped recording right at the very end due to the 15 minute maximum. But I think it gives you a good idea as to what is possible with Google Scripts and Add-ons. Please come and visit me if you'd like to get started so that I can help you accomplish what you want to do.
I had a teacher ask me if there was a way to hide or remove students who are no longer in your class. The answer is maybe. It depends on if they are officially dropped from your class and appearing as red in your roster and gradebook. If not, then no, you cannot remove them until they have been unenrolled from the class. If the student is showing up as red in your gradebook though, you can hide them so you don't have to worry about them. Here is a screenshot to help you do it: