https://userapps.support.sap.com/sap/support/knowledge/en/3431944
3431944 - Some fields are not available in Fiori app F3893 while sales order creation | SAP...
The field "Order" aka COBL-AUFNR at the item level of a sales order is not available in the Fiori app F3893 - Manage Sales Orders V2 during the sales order...