Another two update from Whatsapp now is being released after the latest call waiting feature updated recently for the beta and stable version. It is the privacy group setting and the fingerprint unlock support for the app. This feature allows users to decide who can add them to a WhatsApp call. You can check this out by following this path: Account > Privacy > Groups in the settings menu. The changelog of the new stable and beta WhatsApp updates also mentions the arrival of fingerprint lock feature for the app that was announced back in October. You can enable this feature by going to Settings > Account > Privacy > Fingerprint lock.
The latest WhatsApp update for both the beta as well as stable Android channels brings the call waiting feature. and is now available via the Google Play Store.