How do I replace one level of Rage Powers?

[Techno]

I am working on a new Barbarian archetype that replaces the 2nd level (and only the 2nd level) Rage Power choice with an Extraordinary ability.

When I click on "remove class abilities," Rage Power isn't listed. I assume it is treated different than a standard ability because there are multiple sub-choices. How can I remove only this one level of Rage Power? Thanks!