I created a custom controller inside "Custom\Espo\Custom\Controllers"

namespace Espo\Custom\Controllers;

use \Espo\Core\Exceptions\Error;
use \Espo\Core\Exceptions\NotFound;
use \Espo\Core\Exceptions\Forbidden;
use \Espo\Core\Exceptions\BadRequest;
use Espo\ORM\Entity;

class EntityName extends \Espo\Core\Templates\Controllers\Base
{

public function actionCreate($params, $data, $request) {

/**Data Manipulation **/
return parent::actionCreate($params, $data, $request);

}

}

And i tried to do an actionCreate function which is working but affects the default features of that extension's entity.