In /app/core/Framework.class.php find:
define('ADMIN_FOLDER_NAME', 'admin');
Replace 'admin' with your new folder name.
In /app/helpers/RouteHelper.class.php find:
define('ADMIN_CONTROLLER_PATH',
Ensure that whole line is set as following (do not change the 'admin' part - this is the name of the code directory and doesn't need changing).
define('ADMIN_CONTROLLER_PATH', '\app\controllers\admin\\');
Clear the routing cache by removing /cache/route.cache
Process (uCloud v1.x / YetiShare v4.x)
Rename the actual 'admin' folder via FTP.
In includes/master.inc.php find:
define('ADMIN_FOLDER_NAME', 'admin');
Replace with your new folder name:
define('ADMIN_FOLDER_NAME', 'mynewfolder');
Save and re-upload to your site.