Group Policy - intl.accept_languages

I previously posted this question: https://support.mozilla.org/en-US/questions/1495577 Asking how to use the "intl.accept_languages" setting within the JSON for the new preferences setting within group policy. A moderator posted this as a comment which I have only just noticed: "The value is a string, so it has to be in quotes "en-GB"" - the post is now too old for me to reply. I'm still having issues using this setting even after putting the name in quotes. I've tried: "intl.accept_languages": { "Value": "en-GB", "Status": "user" } "intl.accept.languages": { "Value": "en-GB", "Status": "user" } But neither work, please can someone clarify what exactly needs to be used within the JSON?