Perhaps I'm missing something but I'm wondering if there's a way to either hide or remove the global navigation segment?
If I send a user to a different screen, perhaps as part of a workflow step or a screen dedicated to editing data, there's a good chance I would not want the user to have the ability to click the navigation buttons and leave my sequence I've created. On an Edit screen I could see a user entering updated data and then clicking on a navigation button before saving changes. Users would become frustrated if they lost their changes.
Sometimes screens require we lockdown the choices a user has.