This page allows you to manually split a shipment. From this page, you can or must do the following:
Define the Shipment ID and Shipment Tracking Number for the new shipment resulting from the split operation.
Conditionally assign the Split Shipment ID. This will be assigned to both the source and target shipments. This ID can be used to group all of the split shipments that originated from the same shipment (e.g. via Cascade in Transportation Smartbench).
Specify the quantity or percentage of each shipment detail that will be moved to the new shipment.