Google has added a new secret feature "System UI Tuner" which allows you to make a small handful of changes to your UI. This feature is really in its infancy, and Google warns that it is beta and can cause things to bug out, but I am hoping that Google decides to do more with this in the future. For now it allows you to turn on the battery percentage in the notification bar, add and remove toggles in the quick settings, add or remove icons in the notification bar,and turn on demo mode. To enable the System UI Tuner pull down the notification panel. In the top right hand corner you will see the settings gear. Press and hold the settings gear. It will begin to spin and then it will pop up a notification telling you that you have turned on System UI Tuner. You can find it in your settings at the very bottom of the menu.