Hi daniel, yes, either MIDI Designer must see Reaktor (so it would appear as a virtual destination) or you must use MIDI Designer Initiated Virtual Destinations... but in both cases we depend on Reaktor to connect, too. So you might need to do some configuring, and also starting and restarting apps in a different order.
We don't have Reaktor in the studio, but if you cannot figure it out we'll try to get a copy.
Thanks!
Dan