private function _getCustomConfigOptions(string $dir): array
    {
        $options = ['' => Craft::t('redactor', 'Default')];
        $path = Craft::$app->getPath()->getConfigPath().DIRECTORY_SEPARATOR.$dir;

        if (is_dir($path)) {
            $files = FileHelper::findFiles($path, [
                'only' => ['*.json'],
                'recursive' => false
            ]);

            foreach ($files as $file) {
                $options[pathinfo($file, PATHINFO_BASENAME)] = pathinfo($file, PATHINFO_FILENAME);
            }
        }

        return $options;
    }