Solution : https://service.sap.com/sap/support/notes/736770 (SAP Service marketplace login required)
Key words :
start transaction se11 'abap dictionary', ekkn account assignment table, 'data type' radio button, 'data type' field <, change api function, user-defined fields, data dictionary, transaction snote, component type, choose 'change'
Related Notes :
| 741221 | Inconsistent reassignment of purchase orders |