Android 6.0 is slowly rolling out to devices and it certainly comes with lots of new features that you will want to explore. Some features in Marshmallow are experimental and hidden away unless you decide you absolutely want to, have to, need to, try them out. These new experimental features reside in a preference in the Settings app called the System UI Tuner but you won’t simply see the preference there if you open the Settings app. System UI Tuner, because of the experimental nature of its settings, has to be enabled first. Here’s how.
Pull down the notifications panel. Once the panel is open, swipe down once again until you see the toggles. Once the toggles are visible, you will see a cog wheel icon at the very top (next to the profile button). Tap and hold it for a few seconds and then release it. You will be redirected to the Settings app and an alert will tell you that the System UI Tuner has been added.
To remove System UI Tuner from the Settings app, follow the same steps for enabling it. Once you release the cog wheel icon, you will once again be redirected to the Settings app. An on-screen alert will tell you that the System UI Tuner has been successfully removed.
As for the settings inside the System UI Tuner, remember that they are experimental. Turning them off is incredibly easy but while you have a feature enabled, it may effect your battery life, among other things.
For anyone who likes Easter eggs, when you press and hold down the cog wheel icon in the Notifications Panel, it starts turning. I don’t know if it did that in Lollipop since I never had much cause to hold that particular button down but it does it in Marshmallow and it’s neat to watch.