You will have to request the sound buffer and get the midi. Then change the needed values, and dump it back into the Voyager. I don't know about a direct sysex command to change non CCs controllable parameters in a direct way in some other synths.
The sysex details for a single sound are either available on the Moog pages, or ask Rudi Linhard
(he does the coding for the Voyagers) for it. I am not sure if the document I got here is officially released. Rudi is also answering every detailed questions about the software functions here on the forum.
I noticed that you shared the Moog Editor. I'll try it soon. Thank you!
2-Voyager-edit (links below in the siganture for the Mac and PC version) is not an editor. Have a look here:
You load stored single sound sysex files and the little program check if the will be over write patches when load them into the Voyager (by other software). It will then do a little change in the sysex to route the sound in the edit buffer when saved "Export Sound" and loaded into a Voyager later by other software. So you will be able to test a sound without overwriting your stored patches. And you can save them after loading where ever you like. Or just don'e save the if you don't like the sound.
I don't need a software remote control for the Voyager. It got a real nice hardware user interface. But if you use an RME somewhere down in a rack, it might be useful to do it in a remote way.