I'm relatively new to the Shopify POS app for Android so maybe I'm missing something. But I couldn't, for the life of me, figure out how to return something this weekend. I ended up doing it with a pad of paper, a manual correction to my inventory, and an apology to my customer because I looked dumb for not being able to figure out how to make a return.
Thank God she paid in cash. Not sure what I would have done if it were a credit card transaction.
Victor from Shopify here :)
To process returns on an Android device, you would need the Shopify Mobile App downloaded - You can see more about that here: https://help.shopify.com/manual/apps/apps-by-shopify/shopify-mobile
Apart from that, the only other way would be via your Admin, which you can access through your device's Chrome browser.