To Add attribute in Territory Management

I am trying to add an attribute in 'Create Territory' screen under Territory Mgmt.

I see the 'duplicate row' button and the 'delete' button. But I don't see the 'Add' button. I want to add a new attribute which is SAP delivered.

At a later stage, I want to create a user-defined attribute too. Can anybody give some insight on the above. Will reward..

Thanks,

Ranjan