From reviewing the callback file it looks like there is a hookable event but I’m not sure on best practices for this.
if ($user !== null) {
// Throw hookable event to allow custom application logic for successful logins:
$event = new \Auth0\Laravel\Event\Stateful\AuthenticationSucceeded($user);
event($event);
// Apply any mutations to the user object:
auth()->guard('auth0')->setUser($event->getUser());
}