Creating transport orders from a sales return order

All 3 providers will support the sales return order flow.

The base for creation of the transport order for the sales return order is always Unposted documents.
You can create your Return sales order and wen release you can create the required transport order from the sales return order.
Basically the booking of the transportorder is directly the end of the ShipIt functionalty. When the goods are returned to you warehouse you just follow the Business Central steps to post your return receipt.