Pre-cueing with USB-Headphones

I’d like to use djay on my Surface Pro 5.

My master-audio output will be simply via the headphone jack. I’d like to use USB headphones to pre-cue tracks. While it perfectly works to select between Surface-internal Audio and the external usb device it is not possible to have both.

Any plans to work on that issue? I’d really love to work with that minimalistic setup…