Three nav buttons too little for you? Feel free to add a fourth to make it easier to turn the display off, toggle auto-rotate, or customize the buttons' placement! Here's how you do it:
Go to the Settings, Personalize menu. Tap "Change navigation buttons". Tap a fourth navigation button to add one, or don't select any of the fourth button options if you don't want more than three. Then drag the buttons left and right to re-arrange them to your liking.