From the receipt (its “Distribute to stores” action) the receiving arrives pre-filled and locked — it cannot change, because the lines derive from it. From the list (“New distribution”) nothing is chosen, so selecting the receiving is the blocking first step. This prototype shows the empty state; append #from=RCV-000089 to the URL to see the locked one.

This page saves; it does not submit. Submit is gated by status and lives on the detail page — the shape PurchaseOrderDetailPage.tsx:73 documents for a PO (Draft → Edit header / Submit / Cancel). And the label is Save, not "Save draft", because the status that results is Allocated whenever the grid has allocations: the flip is automatic, so promising a draft would be wrong in the common case.