Solution : https://service.sap.com/sap/support/notes/329205 (SAP Service marketplace login required)
Key words :
additional key words me22n, required entry fields, user exit mm06e005, customer-specific fields, customer exit, purchase order, transaction me21n, transaction separates, business logic, longer controlled
Related Notes :
| 310154 | ME21N/ME51N: Customer-specific check, generating error log |