How to enable multi AWB printing option in WMS 3

This function is only aplicable for WMS integrated courier, and the service provider is allowing this particular function.

First go to Warehouse module, Second browse over to the Carriers sub module now from here click on the edit option of your preferred SLP. 

Once you have clicked on the edit option, carries edit page will be opened for the courier in which you want to enable the Multi AWB printing, now from here scroll down and look for the available service options. Now you need to enable the Support Multiparcel option and click on the Update Carrier.