If back, home and multitasking just aren't enough for you on the HTC One M9, the new Sense 7 gives you the option to add a fourth button.

The ability to add and rearrange the on-screen navigation buttons on an Android smartphone isn't exactly new — but it is new to Sense 7 on the HTC One M9. And it takes just a few taps to get the job done. Here's how it works:

HTC One M9 edit navigation buttons

Adding and rearranging the on-screen nav buttons on the HTC One M9 is easy. First go to the main settings screen, scroll down and choose "Personalize." Then choose "Change navigation buttons." You'll now be presented with all the options you have available. They are:

  • Auto rotate
  • Notifications
  • Hide navigation bar
  • Quick settings

You can only add one additional button, but you can rearrange them in any order you want. Just tap and drag at the three horizontal lines. When you're finished, tap "Done."

The end result will look something like this:

HTC One M9 nav options