Hey Tini, i don't know if you found a solution since you asked about OS X Lion, but i just found one as I had the same trouble : the editor could'nt fin any of my sound card midi port.
I just installed the mmj (Midi for Java) extension that you can find here : http://www.humatic.de/htools/mmj.htm
Simply copy the "libmmj.jnilib" et "mmj.jar" files to /Library/java/extension and the Editor should have access to your midi port. At least it work for me with an Audio Kontrol 1 soundcard. haha just realised that Thorsten posted the link just before. So what works for OS X 10.6 is also required for 10.7