Checking the screenshots of the Soundquest editor may be interesting. The interface is as ugly as it gets but you can see the editable parameters.
You can see that there are two midi modes. One spreads all voices on the keyboard and You can edit for each of the 100 voices at which note it should play. This way you can trigger more than one voice per note. The other mode assigns a voice on each midi channel. It will then play one voice spread across the whole keyboard.
It’s probably possible to switch mode by sysex messages.
https://www.squest.com/Products/MidiQuest11/Instruments/YamahaRX7/index.html