With Hike2 being a CIQ app it doen't support navigation you'd have with a course or rout, but with the available screens, there are a few ways to get "back to start"

one screen has your current location, your start location, and the compass direction to get back to start.

You also got the breadcrumb/map page so you can see where you are and where you started and use that to return to start

If you set waypoints along the way, you can see the distance and direction to each and use this to work your way back to start.