Hello Jian,
manual input is not foreseen here.
In general you can make the settings for the fields control of EWM warehouse requests in IMG activity EWM -> Cross-Process Settings -> Delivery - Warehouse Request -> Field Control. Three you can restrict the number of editable fields per process. But it is not possibe to make firelds changeable that are not foreseen to be changeable.
Best regards,
Katrin