Hi,
I often record instruments with Renoise, hopefully I’m almost always alone, but when playing with friends I can only record 1 sample at a time.
When a I record mono instruments (mic, guitar for instance), I can cheat and route the 2 inputs in a stereo input and then split it in two mono samples, but that’s no more scalable.
I think with some adjustments on the actual record control can handle that. A + button to add more sources, and for each source a new sample output next to the current one in the current instrument would do the trick… ( a little warning if that overwrite an existing one… and go ! )
I have no idea of the complexity of the code behind that… It’s only an idea, I don’t crave for this functionality… So, feel free to bypass 
Christophe.