Aha, found it. It's called Page::print_control_strip(), as it turns out.

Yeah, I was just about to say that the names in the code don't always match the names in the docs. Dreamwidth is turning into one of those Open Source projects that has issues with documenting things properly, either for users or for developers. Anyway, you found it faster than I had time to explain this to you, so.

I still found the name by searching for "navigation strip" on the S2 wiki; the names may be different but they show up close together in the code, so it's easy enough to follow the clues and end up in the right place :-)