Polylang and onepress

I’ve seen in other threads that people have difficulty translating onepress theme with polylang. Nonetheless, I’m looking for a way to use it to translate some text from the customizer, like “Hero large text” for example. As there is a wpml-config.xml file and that those strings from the customizer are registered there (<key name=’onepress_hcl1_largetext’ />), i’m really wondering why i’m not able to use polylang to translate those strings in the “Strings translation settings” panel where simply are not listed. Why !!? Polylang is precisely supposed to be compatible with wpml-config.xml file.
Any help is welcome. Should I add something in functions.php in order for polylang to use that file ? or is there something else in that file that makes polylang not recongnize it ?
Thank you.