Control Transfer of Bills of Product for Preference

Dear Experts,

We are currently setting up the preference processing service for NAFTA (GTS 10.1).

One of the steps to be executed in the customizing, is the Preference: Control Transfer of Bills of Material.

We are facing the issue the field Rule set type (Plug In Customizing on ERP 6.0) is not possible to maintain (Table /SAPSLL/V_TBTGR3 field: PFONY).

How can the field PFONY for BOM transfer for NAFTA be customized?

Please help me to findout the reason, why I am not able to maintain the field.

I look forward to read your thoughs on this.

Thank you for your help.