(Human) Ethniticities
 

I'm trying to figure out where to go to add Ethnicities to the background tab for character creation?

They seem to only be available for Humans, and I can see them for Golarion, as well as for Midgard.

So I figure there must be a way to *add* them, but I can't find a tab in the Editor Tool that seems to correspond.

You create your ethnicities as "Racial Cust Special" (under the Race tab). You may also need a Mechanic (General tab) that lets your race take an ethnicity if you're using a different setting, or your race isn't human.