Creation of returns for ordered items is now possible in the Merchant Center. You can select items and group them in a return that has a tracking ID and a return date. The shipment status of the return is initially either Advised or Returned. Once created, each return item can have its shipment- and payment status tracked individually.
Should you operate with line item states where certain states signify a return, you can add the state role of Return to them. By doing so, items with these states will conveniently be pre-selected when the Return is initiated.