Main mixer and external synth. Outbound CC control..

Hi, kinda newb here. Just dusted off an old 90s Korg X5DR module and trying out Renoise demo (v3 on Ubuntu 16.04).

Although I can control various things via the Instr Midi Control in Track DSP, I can’t change volume or pan of instruments using the main mixer. I changed Instr Midi Control to General Midi to get that working fine, but can’t find anything in preferences to let me see/set/change the outbound CCs for the main mixer.

Any help very much appreciated.