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:
As you prepare your "Emergency Sub Plans" packet for the year, it's a great idea to have a roster available for your sub with the students' pictures. It helps your sub know your students and also ensures that the right students are being marked on attendance. You can view the written directions by clicking here or view the screencast below.
When I talked with teachers about Nearpod last week, there was a teacher at the highschool who really wants to keep his animations within Keynote while having the interactivity like Nearpod. I told him that I'd look into it to see what was possible.