By default sub and sub-sub categories will display on member's profiles, once these have been selected by the member in the Additional Details form:

In order to display only the sub-sub categories navigate to Settings >> Advanced Settings: 

Show Only Sub-Sub Categories On Member Profiles

System Variable: show_subs_member_profile

Once the setting is On, only Sub-Sub categories will show up in the Specialties tab:

For additional questions or help setting this up, please submit a ticket to [email protected] or create a ticket HERE.