@Finnishcoffee: thanks for making that video, it makes things so much clearer.
You’re definitely looking for “record arming”. This is a common feature in DAWs, which lets you indicate which tracks/instruments should receive MIDI input (or audio for that matter). Unfortunately, Renoise doesn’t have that as a built-in feature, so no wonder if you’re feeling a bit frustrated when looking for it.
But the scenario you’re presenting is not too uncommon, and can entirely be scripted. I think the MIDI management console (which you gave a shot) is ready for retirement, as it’s trying to achieve too many things at the same time (some of which has become possible natively with Renoise, such as the stacking of instruments).
Instead, a more focused effort would be to have this (imaginary) tool taking care of the recording arming by going through, and presenting all instruments which are tied to a MIDI input. Then, you could choose to either (1) MIDI assign the record arming directly to some button on your controller, or (2) use the velocity as an indicator. Of course, it should use the routings you’ve specified in the MIDI input panel (or even allow setting them from the tool itself).
It should probably also allow passing MIDI notes onto the currently selected instrument, when dealing with a range of the keyboard which has not been assigned to an instrument, anywhere. That would allow the usual flexibility, especially useful when trying out sounds before explicitly mapping them.
Here’s a quick sketch of what itcould look like: