As soon as the correct configuration profile has been installed from the Apple Developer Center, the new watchOS Beta can be accessed via the Apple Watch App on the iPhone under General to be downloaded in -> Software Update.
To install the update, the Apple Watch must have at least 50 percent battery power and be placed on the charger and within range of the iPhone it is connected to
watchOS 4.3 provides support for the portrait bedside mode, a feature previously only available when the clock was set in landscape orientation. The reason is simple: when Apple launches the Airpower charging mat, the watch must be placed in portrait format.
There is also a new charge animation when the Apple Watch is placed on the charger and a new charge animation Animation while loading the apps. In addition, the remaining battery life is displayed more accurately.
The update of watchOS 4.3 also brings back a feature that makes it possible to control music playback on the iPhone via the Apple Watch’s music application.
In earlier versions of watchOS, starting with watchOS 4, the Music app could only be used to control music that was played on the watch itself. If the tvOS 11.3 beta is installed, there is also the option to control the music playback on the Apple TV with the clock.
Apple plans to release watchOS 4.3 in the spring. Unfortunately there is no public Betas watchOS but only from tvOS, iOS and macOS.