Add a button to cancel a meeting on the join meeting screen

How to add a button to cancel joining a meeting next to the join meeting button from the join meeting screen in the web Iframe?

Welcome to the forum!

What do you plan for the Cancel button to do? At that point, the user has not yet joined the meeting so not sure what you wish to cancel.

Also, do you have your own deployment or are you using the IFrame API to access meet.jit.si? Adding additional buttons with custom behaviour would probably mean modifying and building your own version of jitsi-meet, or modifying static resources within the deployment to mutate the page with JS.