Cant see it anywhere in the manual or on google so i assume it cant be done (or maybe im not searching the correct terms), but for improvising live, i would love to be able to preview new sounds through the headphones only, so i can choose a suitable sound before its incorporated into the main out mix.
Octatrack has cue abilities which is phenomenal for a variety of reasons including hearing stuff before it hits the mains and other routing options (fx send/return). It’s an invaluable part of the OT workflow that adds to the value of this device. Wish the DT had it. However, you can use a DJ mixer or mixer with pre-fader listen option to cue midi tracks before they hit the DT, which is a work around that may be beneficial for your purposes.