Unable to add derivation value on project DFF

Just like for purchase requisitions, we need to have a DFF at the project level (both header and task) that is associated with a table-type value set include a project derivation value. This value set displays a predefined list of values that depends on the legal entity (from related value set setup).For purchase requisitions, it is possible to setup the value set with the parameter "Requisitionning BU ID" (see document How You Can Derive and Validate Descriptive Flexfield Values Using Purchasing Document Header Attributes), but on the project side, the values that could be derived from the page are not available. We have successfully limited the list of values based on the Requisitioning BU ID on the purchase requisition page.