Yes, a seller should confirm the receipt of a product returned to upload an exchange waybill.
[Use API to query a list of exchange requests and check if the pickup status is Returned to seller ('CompleteCollect').]
If the status above is confirmed, use newly issued shipmentBoxId to upload a waybill.
You can upload a waybill up to 10 minutes after confirming the receipt.
An exchange request list query sample will not have shipmentBoxId if an exchange request for which you haven't confirmed its receipt is used as a sample as explained above.