I guess you are referring to languages that do not exist or are not separate in Limesurvey.
But you can always create 'your own' languages. E.g. US vs UK English, you can make a copy of English and create one that is US (or UK), for Belgium French make a copy of French, for Belgium Dutch make a copy of dutch.
However, how we did this back in the day for big international studies, we usually skipped the multilanguage features of the survey tool (not Limesurvey), but rather created separate surveys, because it is often not just the language, but sometimes slightly different questions or answer options. This is the most flexible option. Create one survey per country / language.
But for example for Belgium, despite the two languages, they health system should be the same, so you could have one survey with dutch and french for Belgium. Same for Canada.
So depending on how different the questions and answer options between countries are, I would probably go for 1 survey per country.
I answer at the LimeSurvey forum in my spare time, I'm not a LimeSurvey GmbH employee.
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