This functionality is new as of version 4.0.
They can be added to a Delivery one at a time; or, by clicking the ‘Add All Items’ button.
Refer to Add Delivery Item.
To Add All Purchase Order Items to a Delivery:
Navigate to the 'Purchase Order Details' screen → 'Delivery' tab.
Clicking the ‘Add All Items’ button.
This will add all Purchase Order Items that have not already been received, to the Delivery.
If an incomplete Delivery is not available, add one by clicking the ‘Start New Receiving’ button on the 'Purchase Order Details' screen → 'Purchase Order' tab.
An incomplete Delivery will not have ‘(Auto Stocked)’ in the tab label.
Refer to Start New Receiving.