Custom variables defined in extensions

You can define

bootstrap.php extension file sketch

...
public function run()

    $dispatcher = erLhcoreClassChatEventDispatcher::getInstance();
    
    $dispatcher->listen('chat.dynamic_array', array(
        $this,
        'dynamicArray'
    ));
}
...

// Listener in the same class
public function dynamicArray($params)
{
    // $params['chat'] present chat objects 
    $params['dynamic_array']['player_class'] = 'dummy'; // {args.chat.chat_dynamic_array.player_class}
}