There isn't a easy way to do this like a configurable value but yet you can still do it editing 2 files. First of all make sure that the admin folder has been renamed and then open includes/chevereto.php and change this:
PHP:
define('__CHV_FOLDER_ADMIN__', 'admin/');
To this:
PHP:
define('__CHV_FOLDER_ADMIN__', 'xxx/');
Then open includes/classes/class.handler.php and change this (it appears two times in this file, change both of them):
PHP:
$this->base_request!=='admin'
To this:
PHP:
$this->base_request!=='xxx'
And you will have moved the admin folder. I will enable this as a configurable option for 2.4