You want to use extension fields, for example WBS Element, for API_FINWBSELEMENT_SRV and API_FINPROJECT_SRV, but this is not possible.
- SAP S/4HANA Cloud
These two API are not released to customer, just for SAP internal use only. There is no extension fields provided in original design.
Please always check in the API Hub (https://cloudintegration.hana.ondemand.com/) for standard released API.
extension fields, API, WBS Element, Project. , KBA , FI-FIO-GL-IS , Reporting Apps , Problem