MultiTerm 2019: Missing sublanguage

I tried to create a termbase but the sublanguage I need it not available.

I need English (Switzerland). This culture (en-CH) has been only recently added to Windows 10. Maybe that’s the reason it’s not available in MultiTerm?

When will it be available? How do I add it?

I need it because I use the sublanguage in Trados and my company’s authoring tool.

Thanks for your help.