A real DX7 can almost completely synchronize with a software editor or other devices by SysEx. This works, as any changes made on the DX7 are passed back via MIDI SysEx messages of two types, if sysex transmission is enabled on the DX7 menu.
Two DX7’s connected to each other would perfectly synchronize on voice selection and parameter change:
-If a different voice is selected, the voice data will be send as SysEx paket in addition to the MIDI program change event. So the other side can synchronize it’s voice data shown to the one stored and selected on the DX7.
-If a parameter is changed, a parameter change SysEx will be send.
Currently MicroDexed receives both of these messages, if I am right. But it transmits none of them.
So any software UI would only work in one direction. Editing a voice is cumbersome, as we always need a copy of the voice on the PC as long we can only send it out. Changes made by the MicroDexed hardware UI won’t reflect on the PC side.
The original Dexed already implemented this with some ceveats.