Hello,

Plugins caring about multilingual generally add a file name wpml-config.xml in their root directory. This file allows, among other things, to add strings stored in options to the string translations table. The nice thing is that it’s compatible with both WPML and Polylang.

When the plugin doesn’t provide such file, you can create one for your own install and add it in wp-content/polylang (not in the Polylang plugin directory) or in in your child theme directory.

Here is the doc for this file: https://polylang.pro/doc/the-wpml-config-xml-file/