This site names this specific bonus guide directly as Bonus 2: the Power Challenge.
This site describes it directly as a short daily-action plan of simple habits — worth reading it as a habit-formation guide, distinct in scope from the relationship-focused guides among the other four.
Worth noting this site separately publishes its own five-habit list directly on its homepage, free of the bonus guide — worth checking whether the Power Challenge overlaps with or extends that publicly stated list.