Auto Return isn't actually useful to configure with PayPal Express and Shopify, since the customer can be taken through one of two different paths of the checkout:
Either way, they'll be directed back to your store to complete the purchase, then on the order confirmation page, there's an automatically generated link to return to your storefront. Auto Return becomes more important with other PayPal checkout services.
Hi Alek, how is the return URL determined? We have the problem that our page is translated with the App weglot and via paypal express checkout customers are coming back to the wrong checkout language. e.g. they are surfing in german language and via paypal they end up in the english checkout .... whereas the cart was still german. many thanks for your help!