How to enable Task-Level DFF from PPPM Visible in AP Invoice Lines and PO/Requisition Creation

Summary:

The requirement is to make a task-level Descriptive Flexfield (DFF) created in PPPM visible in AP invoice lines and during purchase order/requisition creation. The intent is to allow users to view the task-level DFF value without requiring them to enter or select it manually.
Alternative approaches such as using cost collection flexfield and work types were evaluated; however, they do not meet the requirement. Cost collection flexfield enforce mandatory user input, which is not desired, and work type—although defined at the task level—is not natively available or exposed in AP invoice lines or Procurement transactions (PO/Requisition).