So I'm playing around with trying to create some multi-instrument presets with combi-mixer. Maybe the JSON can be used here.
As Andi pointed out, most of the difficulty is related to getting mixer settings from one instrument to another. We can build a dimension tree with any combination of "patches" we want, but the actual mixer settings such as EQ and other things, are contained in the overall inst preset, which is saved in a binary format and I can't find any way to produce a JSON configuration of the overall inst preset. We can get the JSON for each slot (and its descendants). But slots only seem to contain either references to patches or various edit and performance attributes. Nothing about the mixer is in that JSON that is available with right click copy.
It is however possible to save a user mixer preset. So open each instrument preset that is intended to be combined into a single instrument preset. For each one, save the mixer preset. After that go open them all and try to figure out how to combine the JSON from several into one mixer preset.
That will not be for the faint of heart though, but it might be possible. Might be able to write a javascript script to do it.
Its probably easier to just open each of the intended instruments in another synchron instance and then approximate the EQ settings in the combined one, one strip at a time.
if there is some other way to do this already in an easy way, please advise.
(note, would be nice if there was a "Copy Channel Strip Settings" command or something, and could then copy and paste from one instance of Synchron to another; and build up combi multi-instruments that way, or at least easily add slightly different instrument family groups to a single synchron instance with a combined mixer when needed)