IDoc: Post Goods Receipt on RMA (Return Delivery)

Dear experts,

We create a Customer Return order and an outbound delivery in SAP manually. The outbound delivery is sent to our 3PL.
Now when the 3PL receives the goods in the warehouse they send back an EDI picking confirmation file.
My question is which IDoc can I use to post the Goods Receipt on my outbound delivery?
I can manually click "Post Goods Receipt" but I am wondering about the IDoc type.

I tried posting the GR with a WHSCON Idoc but it only works if the Delivery has a batch maintained. But the batch will be empty in the Delivery and sent by the 3PL.

Is there a possibility to use a MBGMCR IDoc to accomplish this?

Thank you,

Peter