Swiss German Spell Checking is set to German for ß instead of ss

I’m writing Text in german (Switzerland) where we use “ss” instead of ß which is common in Germany. Example: gross instead of groß. (big)

On my Scrivener on Mac the swiss rules are applied. On Scrivener on Windows it’s complaining that “gross” is meant to be written “groß”. This bothers me.

The Windows System works fine for this, as it is set to german-swiss. In Word (or any other application) the spell checking is applying swiss rules.

I’ve also only downloaded the spell checking files for “German (Switzerland-de-ch)” in Scrivener, the dictionary is running fine.

Is there a way to change Scrivener in Windows to run / check as “swiss german”.

Thanks for any hints.