There are four user fields which can be displayed in the inflow-outflow tab of the order recommendation. These user fields can be defined in MRP Scenario > Detail > Pegging and Replenishment >Sales >"Sales Order and UDF for Sales Order and Reserve Invoice"
See MRP-Sales-Pegging settings
In above displayed screenshot we choose an UDF of item master data (table: OITM) which has to be displayed in the order recommendation.
The following screenshot shows how to display this field by using the "Window Settings" functionality:
