Item level User Fields appear on the User Fields tab in Maintain > Inventory for each inventory item. These fields can be set up in User Definable Fields.
When the two Preferences settings “Use line item information in StarShip database” and “Save line item information in the StarShip database” are checked in your setup, User Definable fields will be updated and used based on the shipment line item data (whether imported from the Source document or typed on the screen manually).
If only “Use line item information…” is checked, the user-defined fields will be read from StarShip’s inventory but not updated.