Under the Korg page of Synth Zone, scroll down until you see Trinitro (by Kevin Goodman). It's good, constantly being improved, shareware and only $25 US. ALl updates are free. It only does the Trinity.
Another editor for the Trinity is made by Sound Quest. Called Midiquest version 7.0. Does bunches of synths and modules. Certainly more expensive but a very good program designed by a great bunch of guys in British Columbia.