The new mute segments allow you to mute a section of a video instead of skipping it. This is useful when there is something that needs be skipped in the audio, such as an audible sponsor message, while the video on-screen is important. This will also be able to be used to remove those annoying bell sounds that are sometimes added for reminding people to subscribe.
This new action can be used with Sponsor, Unpaid/Self Promotion and Interaction Reminder.
One other cool thing I have noticed with this is that mute segments can get even more precise than skips. With skipping, the browser sometimes acts up when it skips a very short amount of time, making it a better experience just to not skip it at all. With muting segments, it feels a lot smoother and you don't really notice the muting happen.
As with normal segments, you have the option to unmute at any time to hear what is actually happening.