It was added there by using the "Additional HTML" feature.
Site Administration -> Appearance -> Additional HTML
The code is placed in the field :
But in the Boost theme, it doesn't show in the header menu. It shows directly below it. On the login screen, I think it is a little tacky. But the method saves the menu usage on the top as the Boost theme moves the menu to the footer on smart devices - responsively. It is a real pain for our students to have these addition links all the way at the bottom.
I'd customize the Navigation menu if I could.