Up to five WhatsApp chats can be pinned to the top according to the concept

One of the best methods to provide input on a new feature in the WhatsApp beta for Android, iOS, and Desktop is with a concept. On WhatsApp for Android, iOS, and desktop, the ability to pin chats to the top of the chat list was first offered a number of years ago.

Users may easily access their most crucial chats by keeping them at the top of the screen thanks to this functionality. While pinning 10 chats may be too excessive, we think that a new maximum of 5 pinned chats is an acceptable compromise. Many users have requested the ability to pin more than 3 talks to the top of their chat list.

Additionally, it is reasonable to allow a higher limit of pinned chats in order to better serve the demands of users who are increasingly using larger screens. The number of pinned chats must be increased in order to continuously improve the user experience for all users.
Unfortunately, since this is only an idea, it won’t actually be included in a future release of WhatsApp.

Read more here