Lots of workarounds for this, but it sure sounds like you could just use the MTK12 for this, simply plug both synths into it and select the 'Ports' in the Audio Interface
Preferences - Audio - Driver button .. (again holding CTRL while selecting drivers allows multiple inputs channels)

However -
Recording a Live band with multiple inputs sometimes requires submixes (ie, the DAW has 8 available inputs and I have 12 to record)
Sometimes a submix (as JOM suggested) is the quickest way to get 'er done.

Temporarily 'borrowing' inputs
You may have to accept 6 drum mics as a stereo mix in order to also record guitar & bass, etc.
But you can also always go back and record those drums to separate tracks as inputs from the device if needed ..

Last edited by rharv; 08/12/24 03:34 PM.
I do not work here, but the benefits are still awesome
Make your sound your own!