I feel like this is a dumb question. I got my Keyboard.io from the original kickstarter but just got around to trying it out.
I couldn’t find this from search.
The windows key is labeled Cmd physically in the default layout, which is the Mac term for it.
In code it would be called Key_LeftGUI, I don’t know about Chrysalis but it might call it Super Key which is a Unix term for it.
Oh if you are referring to the atreus and not the Model01 then it is physically labeled Super