WhatsApp Beta for Windows Phone has seen one more update and the latest update brings better notifications management and notification expansion for better viewing.
You can now expand the notifications to see more lines of text than before, as can be seen in the above screenshot. May be one step closer to interactive notifications.
You can also see the full list of notifications received in Action Center and it clears out when you open the app. So it solves the current issue of notifications staying unmoved in Action Center even when you have opened the app. The Live Tile also shows number of received messages now.
Then new version is 2.12.264. WhatsApp keeps pushing new features and improvements to its Beta app and we can expect these changes to come to stable version soon.
Thanks Pedro for the tip. Cheers!!