You can mark WhatsApp chats as read or unread without opening them at any time you want.
You can mark the chats that you want to read later as unread. Keep in mind that marking chats as unread will not affect the recipient device. In other words, it'll only make changes on your device alone and not on the recipient device.
However, marking chats as read (which marks all the messages as read) will make changes on the device of yours and recipient.
with that said, let's see the steps to do these tasks on Android.
Mark Chats as Read on WhatsApp
That's all. The chats are marked as read.
Mark Chats as Unread on WhatsApp
That's it. The chats are marked as unread.
I hope that this guide is useful to you. If it is, share this guide with your friends.
How to Mark WhatsApp Chats as Read or Unread