code: static public function transCustom($path, array $parameters = [], $locale = null) {
          $dict = static::getInstance()->custom_dictionary_name();
          $path = '.' . ltrim($path, '.');
          $primaryPath = $dict . $path;
          $trans = trans($primaryPath, $parameters, $locale);
          if ($trans === $primaryPath && $dict !== 'cmf::custom') {
              $fallbackPath = 'cmf::custom' . $path;
              $trans = trans($fallbackPath, $parameters, $locale);
              if ($trans === $fallbackPath) {
                  return $primaryPath;
              }
          }
          return $trans;
      }
docs: Translate from custom dictionary. You can use it via CmfConfig::transCustom() insetad of
  CmfConfig::getPrimary()->transCustom() if you need to get translation for primary config.
  Note: if there is no translation in your dictionary - it will be imported from 'cmf::custom' dictionary
  @param string $path - without dictionary name. Example: 'admins.test' will be converted to '{dictionary}.admins.test'
  @param array $parameters
  @param null|string $locale
  @return string|array