Did you know that Android has a secret menu for customizing your phone's system user interface?
It's called the System UI Tuner and it can be used for customizing an Android gadget's status bar, clock and app notification settings.
Introduced in Android Marshmallow, this experimental menu is hidden but here are the steps to unlock it.
Unlocking the System UI Tuner
To turn this feature on, swipe down from the status bar to access your Quick Settings panel then hold down the Settings gear icon in the top-right corner. If executed correctly, your Android phone will vibrate and a message will appear saying that you've successfully added the System UI Tuner to your Settings.
Here you can do nifty user interface tweaks like selecting what icons show up on the status bar or have the battery level display while charging. You can also switch your clock to show hours and minutes plus the seconds, if you desire.
You can have the Do Not Disturb toggle show up with the volume bar or turn off the volume shortcut for it.
One other useful toggle is the Power notification control. With this you can set different notification levels for each app, ranging from Level 0 (block all notifications) to Level 5 (highest importance).
Currently, there's also an option to enable split-screen by swiping from the app overview icon.
How to turn off the System UI Tuner
Beware that these System UI tweaks are experimental. As the System UI Tuner warning states:
"System Tuner gives you extra ways to tweak and customize the Android user interface. These experimental features may change, break, or disappear in future releases. Proceed with caution."
To remove the System UI Tuner and any tweaks you have made, swipe down from the status bar again to access Quick Settings then hold the Settings gear icon again until your phone vibrates.
A prompt will then pop up asking if you want to "Remove System UI Tuner from Settings and stop using all of its features?" Select "Remove" to clear it out.
Alternatively, you can just simply go into the System UI Tuner menu, tap on the three vertical dots located in the upper-right corner then select "Remove from Settings."