If you want to show your appreciation for someone’s message or photo in a WhatsApp group chat but don’t want to bother everyone in the group with a notification of your reaction there is now a way by simply long tapping the thing you want to react to and selecting your emoji reaction.

This was a feature request raised over 6 years ago but better late than never I guess!

https://www.quora.com/Why-doesnt-WhatsApp-let-you-like-someones-message