It's easy enough to have a return to start (making it odd to not have one).

With the Garmins, one can drop a pin (location) at the start (somewhat weak because you have to remember to do that). You can also scroll the map to your start and drop a pin.

The Garmins (with maps) can calculate routes to locations.

There should be an option to calculate a reverse course.

One can always follow the cyan line (your recorded track) back to the start.