I’ve opened a bug for German (Switzerland) as it looks like it’s supported, but missing from the options menu: Supported spellcheck language not available through the options menu
French (Switzerland) doesn’t seem to be supported at the moment, as I wasn’t able to add “fr-CH” to the Preferences file. And even if it was, I’m not really sure how I’d verify that it’s working, because the Swiss words such as “septante” and “huitante” aren’t marked as errors when using “French (France)”.
Thanks for the help everyone.