All you have to do is select a message and tap on the 'Reply Privately' button accessed from the three-dotted button in the upper-right corner.
This will quote that message in a private chat window with its sender.
Vacation and Silent Mode
With these two features, WhatsApp is giving options to determine how muted chats are handled on receiving a new message.
The Vacation Mode, for instance, has been designed to keep muted archived chats in archive even when a new message is received.
It is still not available, but the Silent Mode, which hides notification dots for muted chats, is being rolled out for Android.
Picture-in-Picture for video
Back in October, WhatsApp for Android beta (v2.18.301) enabled support for picture-in-picture or PiP.
The feature, as the name suggests, lets users watch YouTube, Facebook, or Instagram videos by staying in WhatsApp itself. It doesn't direct to another app for playing content and makes WhatsApp even more seamless.
Notably, iOS users have already been using this feature since January.
Swipe for quick reply
In another reply-related feature, WhatsApp has brought swipe-based gesture.
Now, any iOS or Android user can quickly respond to a particular message by right swiping on it.
This will quote the message in the text-box, just like how it happened when users had to long-press a message for sending replies.
The feature came to WhatsApp for Android (beta v2.18.300) months after appearing on iOS.