The official beta version of WhatsApp received an update in which the Edit feature was enabled by default. But, it is said that the features were accidentally enabled on the WhatsApp Android Beta Version 2.17.26. It is accessible by selecting a message and then tapping the menu (the three dots in the top right corner). The leak was first mentioned in the famous WhatsApp leaker WABetainfo.
But, nothing happens on the clicking the edit button. It is assumed that the function is still under development and need some changes from the server side from the company. And also the edit function update was disabled by the new version 2.17.27 the very next morning.
Other features available to the WhatsApp Android Beta Users are the revoke function that enables the users to revoke the messages from the conversation as if it never existed, although it will work only if the recipient has not seen the message.
Another feature is the change in the Status UI.
As I mentioned before, these features are only available to the beta users of WhatsApp Android app.