For those who are looking for having extension parameters in BAPI_ALM_NOTIF_CREATE please implement below 2 SAP notes in the order mentioned.
1. 2151416 - Preparatory note for SAP note 2108975
2. 2108975 - Maintenance of customer fields using BAPIs of the maintenance notification.
You can implement these automatically. For first note only 1 manual task is there to execute the program generated after implementation.
Regarding how to use BAPI extension please refer Update extension QMEL ( CI_QMEL ) by function | SCN.