When I open on my Mac the Fonts window (not Font Book, but for example in TextEdit > Format > Fonts) it shows by default the fonts in my language (in my case “Deutsch”). All Fonts generated in Glyphs wouldn’t show up. Is this a fonts settings problem or a Mac problem?
Not sure what that group is made of? Fonts that support German? Or ones that have localized names?
I do not know either
I believe it checks for an available Unicode values. Possibly it requires the cap sharp ẞ.