New Middleware filter condition for CUSTOMER_MAIN

For the R/3 adapter object CUSTOMER_MAIN (and CUSTOMER_REL), the SAP documentation suggests that a new filter can be added by maintaining the SMOFFILFLD in CRM and the corresponding CRMFILFLD table in ECC. We wish to add KNA1-KTOKD (Account Group) as a filter criteria. We were able to add the filter in CRM (SMOFFILFLD through SM30). However, our ECC6.0 implementation does not provide a standard SM30 maintenance for this table. Is there a way to add this entry in our ECC table?