People have requested polyphony a lot here, and it’s an obvious request that would open up the device so much.
However, to the product team (hopefully) reading this thread, I’ll just try to make it easy for you as a stepping stone towards polyphony: allow the ability to “link” tracks together so that when you modify a parameter (let’s say the filter cutoff) on either of the linked tracks, it will affect all the linked tracks in the same relative amount. Sort of like a more narrow ctrl+all - i.e. a ctrl+some.
That way I can at least program my chords or polyphonic melody lines across two or three tracks like I do today, and still do things like filter sweeps etc without having to resort to external midi controls or the more dramatic ctrl+all sweep.