You may add new Listing Types or Property Types or Fields or new location names such as new countries, provinces, etc in your WPL. Therefore you need to translate them as well if you have a multilingual website. WPL PRO has a feature for generating dynamic strings in a single PHP file located in /path/to/plugin/languages/keywords.php
For generating dynamic strings go to WPL->Settings->Languages and click on the "Generate WPL dynamic strings for using in translation plugins like WPML" button.
Then use one of the following approaches:
1- Rescan WPL strings using the "WPML String Translation" plugin if you're using the WPML plugin.
2- Add /path/to/plugin/languages/keywords.php keywords into your .po file (using some tools like this) and translate dynamic strings and then upload a new .mo file in the language directory.