The DHL Versenden module for Magento 1 does not support true multipack shipments, because DHL's webservice does not provide this feature.
Therefore, the button for adding packages is disabled in the DHL popup.
To split a shipment into several packages, you need to create several Magento shipments:
- Before creating the shipment, set the quantity for some items to zero (see screenshot below).
- Note that this must not be done in the DHL popup, but before it is opened.
- Then activate the checkbox "Create shipping labels" and confirm the shipment.
- Now the DHL popup appears. Add all items here, and select the desired DHL services.
- Confirm this to create the DHL label.
Repeat these steps for each package to get several DHL labels (one per package).
Excluding items when creating a shipment
In the DHL Shipping module for Magento 2 it is possible to add packages in the popup.
However, this is because Magento 2 handles the shipments differently. The resulting DHL labels are still not true multipack shipments.