Starting today, bol.com offers customers the option to return multiple items in one shipment, using multi-item returns. This functionality is described on https://partnerplatform.bol.com/verkopen/retouren/retourmelding.
There is no impact on the API v2 and v3 return endpoints, which you can still use to handle your return items.
With multi-item returns, an extra identifier will be provided on the shipping lable and the packing slip, to make it easier to retrieve return details. We are currently working on making this id available in the API. When available, this will be published on developers.bol.com.