This shows that the social networking giant can work on a pilot to combine WhatsApp into its Facebook app. This special button can be found in the menu area. If you happen to be one of the users in the control group it should appear at the top just below your name. But not everyone can see it.
Facebook probably has a goal to further increase WhatsApp's user base, which is still struggling to gain traction in the United States and other Western markets.
Additional information, This is not the first time a company has tested this type of feature. In 2015, Facebook tries to include the WhatsApp send button in the Facebook app, which allows users to share photos with their contacts without having to leave the app.
It's possible that some people are waiting for these shortcut keys to be launched to all users in the coming months based on the opinions they get for the same. However, it is uncertain whether anyone will be able to use this application and we need to wait for the company to declare the official stipulation on the same.
