The new version of WhatsApp has the ability to join existing audio and video calls. Previously, to do this, you had to end the conversation and create a new one with an updated list of participants. In addition, users who have left the call (whether independently or due to problems with the quality of communication) will now have the opportunity to return.
After the update, the “Calls” tab will display all active calls that you can join. Before you join, you will have the opportunity to see who is already on the call and who else has been sent invitations.
The feature is being rolled out gradually on all platforms. If it is not available to you yet, you will have to wait a little longer.