Create Z attributes in Standard BOL Object

Hi community,

Anyone knows how can i add a new custom attribute in a standard BOL object manually or step-by-step? The new fields are not possible to add by AET or EEWB because the BOL object is not available.

In my specific case, i want to add two fields in object BuilSEPAMandate.

Also, some BADI should be raised to fill those fields in DB...

Thanks,

André Mendes