Solution : https://service.sap.com/sap/support/notes/324628 (SAP Service marketplace login required)
Key words : 
customer-specific master data fields, additional key words rkaep000, prerequisites customer-specific fields, commitment line items reports, enter data type = kaep_coac, master data fields, line item reports, line item report, report/report interface, standard data elements
Related Notes : 
       
| 896531 | CO-EP reports: Customer-specific authorization checks | 
| 325546 | CO line item reports: Creating a user-defined field |