Video Player Settings
This section appears in the Master Audio game object if you are using Unity 2019.3+. If you are using Unity Video Players, you can drag them into this section to allow Master Audio to control the audio of them. The section looks like this initially.
If you drag any Video Players into the yellow drag area, you will see a specially named Sound Group created in the Mixer section named "_VideoPlayers", which cannot be deleted. It also creates a Bus of the same name, which can't be deleted either. After adding a Video Player, your Inspector may look like this:
Unlike most Sound Groups and Buses, most properties on these special ones cannot be altered. You can't preview anything or stop any audio playing or assign Bus Voice Limits, but you can solo, mute, and change volumes of the Group and Bus, as well as assign the Bus to a Unity Mixer channel. Keep in mind that Master Audio will only control the audio of the Video Players you tell it about using this section.