The feature is called Vacation Mode.
At the moment group chats can be muted, which means they don't send you notifications when new messages arrive.
However they do show as "unread" messages both in the main window and, on the app icon itself.
When the feature is enabled, any chats you have muted can be archived and won't show as unread within the app, or on the icon.
So if you in one of those busy groups that you don't really enjoy reading, but that leaving will offend someone or other, then this is ideal.
Once WhatsApp gets updated you'll need to do the following:
Find the group chat you want to be silent and mute it.
On iOS this is done by swiping left on the message. On Android this involves pressing and holding a message and waiting for the icons to appear at the top of the window.
Once you've muted a chat, you can then archive it. On iOS, again, this is done on a left swipe.
On Android press and hold a message. Once archived the message thread will go away until a someone sends a new chat message.
With the feature you'll be able to enable "Vacation Mode" at this point and any new messages that come in won't move the chat out of the archive, reports the Mirror.
Of course this does mean that for chats you need to keep up-to-date with you'll need to manually head to the archive to see if they have new messages. You can also turn off the vacation setting and new messages will appear again, resurfacing the chat thread.
It's also nice to know that chat messages won't give you a message count on the WhatsApp icon, which means you'll only ever be told about messages you want.
It's not clear yet when this feature will launch, but it shouldn't be too long.
After all, users have been after this functionality for absolutely ages.
