There's no obvious way to get to the Documentation space.
Summary: There's no simple button or action that will take me to the Documentation space.
Should Space Owners perhaps be invited to that space by default, at least in a read-access fashion? Then it would at least show up in My Spaces.
Justin: interesting point. I suspect that the right approach is something to do with the "Favorite Spaces" mechanism I'd already been toying with -- a way of marking Spaces as Favorites even if I'm not a Member. Then we could automatically make Documentation a Favorite, and you can take it out of the list if you prefer.