First read the OSS note of reference: 1156325 - BAdIs in the Logistics Invoice Verification environment.
- Within the docuemnt, look for MRM_ITEM_CUSTFIELDS, so you get guide on how to add customer fields in database, structures and detail screen > Append customer fields to table/structure and implement the BAdI.
- Then transaction OLMRVERDLIST > Add your own display variant to the list for MIRO - SAPLMR1M - 6310. (copy a standard one and adapt)
Regards,
Raymond