When you confirm the order, a delivery document for the ordered goods will be automatically generated:
Go to this document:
The warehouse movement displays two columns: the ordered quantity of goods ("demand") and the actually shipped ("quantity"):
In the "quantity" column, indicate the volume of goods shipped in the first stage:
Confirm the document.
The system will offer to create a reorder (a document for additional shipment of the undelivered part of the goods). Click "Create reorder":
If you go to the order, you can see that there are already two warehouse movements:
Next, you can proceed to the second movement (second delivery) and confirm it: