macos - How can I remap “Alt”+“Gr” key combo to the Win key in Mac OS X on a Yogitype keyboard?

I have a Yogitype keyboard with a Windows keyboard layout but I’m using it in Mac OS X.

I basically would like to know how to map a modifier key to a non-modifier key, but specifically: How do I map the Alt Gr key to the Windows key (The equivalent of the Mac Command key)? The regular Win key is in a very inconvenient place.

I tried to do this in Ukelele, but I could only figure out how to remap the characters that Alt Gr provides as a modifier, not the Alt Gr key itself. I don’t really care about those characters at the moment.