On Bags By Delivery Date or the Bags Report, click the action button on the bag's row: Mark Bag Delivered for an En Route bag, or Mark Bag Returned for a Delivered bag, and confirm "Are you sure?". The page reloads with the new status. The same buttons exist on the bag's own page (opened by scanning its QR code) and on the customer's order page, provided Business: Labels > Bags status : Show mark delivered/returned button is Yes and you're logged in as an admin.