The header data in SAP Fiori used to be divided into several sections that could be selected out of a dropdown list (Basic Data, Payment, Details, Vendor).

The drop-down list with the header data sections has been removed. Now, only the first section of the header data (Basic Data) is displayed in full. The remaining sections can be viewed by clicking on See More.

If there can only be one supplier, the Vendor section is not displayed. If there are several possible suppliers (for a complex booking), the section is displayed.