The WhatsApp development team has started testing a new feature that will let users pin chats in the Android version of the chat app.
Pinning a chat will result in it appearing at the top every time, reducing your time and effort that would have otherwise gone into finding it. This feature will come out handy for people that with very long chat list on WhatsApp.
The feature, which is currently available in the beta version (2.17.162 or 163) of the app, lets you pin a maximum of 3 chats. If you try pinning a fourth chat, the app will display an error.
If you wish to join the WhatsApp beta program on Android, you can do so by clicking your way to the Join Beta here.