Mark as Read:
This feature lets you mark read to your unread messages.
How it works:
Click on chat of unread message you will see a dropdown where you can click on mark as read.
You can also mark the messages as read from the unread messages section. To access them click on the bell icon and it automatically shows you all the messages.
Marking messages as read serves the purpose of marking those messages read which you have read and separating them from the list of unread messages.
It saves time and segregates the message, once read. Keep your chat screen clean and sorted by only showing the unread messages on top.