Apple has just released iOS 9.3 beta 3, exactly two weeks after the release of the previous second beta, for developers. That update brought a shortcut to Night Shift Mode to Control Center, on top of a bevy of other new features.
Just got to Settings > General > Software Update on your iOS device to get the over-the-air update. The standalone downloads should be making their way into the Developer Member Center soon, along with other beta updates to tvOS and watchOS.
…more to follow