Solution : https://service.sap.com/sap/support/notes/388065 (SAP Service marketplace login required)
Key words :
individual account assignment lines manually, additional key words mir7, 'gr-based invoice verification', multiple account assignment, account assignment line, customer exit exit_saplmr1m_002, partial invoice, purchase order, dialog box, green arrow
Related Notes :
390408 | MIRO: problems with customer exit EXIT_SAPLMR1M_002 |
138957 | MIRO, MR1M: Default values for the account assignment items |