When you scan the returned package label

1.) GLS Slo

read tracking number and found ''order number'' will be displayed on the mobile scanner

When you scan the next packages, they will be added to the list

When you have finished scanning the returned packages, click on Confirm returns so that the status of the orders will be changed to ''Package returns'' and a credit note will be created. 

In the additional settings, you may configure the order status, which could be read by the mobile scanner to create package returns.