This feature has been spotted by WABetaInfo — the online platform that tracks the upcoming features and changes on the Facebook-owned app — in the latest Android beta version 188.8.131.52 of the app. The report states that since currently this feature is under development, it is not yet available and will in a future build.
As per the WABetaInfo report, this feature will allow users to mute videos before sending to a contact or adding it to their status updates. The screenshot in the report shows that the option to mute the video will be available after users select it along with all other editing options such as trimming, adding text, emoji, etc.
Readers must note that while the feature has been reportedly spotted for Android users, it is expected to be rolled out to iOS as well as web users.