How do I create a template with several smaller templates to plug in as needed

Your third option sounds the closest to what we're looking for but copying and pasting each necessary section is what we're trying to avoid. Trying to make this a little user friendly. There are several different types of cases we implement with multiple different moving parts a lot of which we're looking to have plugged in. For example our main template would be a general outline of tasks for a new enrollment, but this particular client is paying for technology services and onsite counseling. But another client is doing a re enrollment with phone counselors and consolidated billing. We want to have templates for each set of tasks for separate services to be able to easily plug into each case where they belong. We're trying to see if there's a way to avoid going out into another sheet and copy/pasting each and every one of these sections per service