Forgot to mention that I'm currently using ISE 1.1.3. I fround the following in the new ISE 1.2 documentation:
Cisco ISE also creates dictionary defaults for the IETF RADIUS set of attributes that are also a part of
the system-defined dictionaries, which are defined by the Internet Engineering Task Force (IETF). You
can edit all free IETF RADIUS attribute fields except the ID.
Cisco ISE also creates dictionary defaults for the IETF RADIUS set of attributes that are also a part of
the system-defined dictionaries, which are defined by the Internet Engineering Task Force (IETF). You
can edit all free IETF RADIUS attribute fields except the ID.
I'll upgrade and see if I can edit the attribute that I need.