Update Sales Order line EFF through FBDI

Hi Folks,

Context:
The customer creates or imports sales orders through FBDI. Every night, a priority number is passed by their DRP (Distribution Requirements Planning) system for each order line. This priority number needs to be updated in the Sales Order (SO) line's EFF (Extended Flexfield). This value will subsequently be used by Backlog Management for rescheduling and prioritization.

Question:
What are the necessary fields (sample FBDI spreadheet) that need to be sent to update the Sales Order (SO) through FBDI when using the profile option "FOM_IMPORT_VIA_REST_BACKEND"?

I would greatly appreciate your inputs and expertise on this matter.