There is some code for it but I'm not sure how far along it is. I don't think the Cocoa UI is very useable yet though.
In fact, at one time it was usable, but it has gotten less so, assuming it even still compiles.
The last I looked at Yi on OSX (about 3 months ago) it fails to recompile due to an incompatibility between Haskell package Dyre and the OS. So you can use it but never configure it.