As far as I can tell, you cannot export as a wave file what a cue mix sounds like
This would be useful as when you have a session with the control room setup and various cue mixes going to people - you already have a great mix for the musicians to get practice tracks. For instance, when I record a band, I give them their mix (without their instrument) and then they take that mix home to rehearse to. EG, So a drummer can get an export of the track with no drums, bass and click nice and loud, and vocals/guitars pushed back in the mix, the perfect way for him to rehearse the track on his own
So when you choose to export a track, it would be nice to see “Cue mix1-4” as an option on the channel list, this way you don’t have to create a whole separate send just to get this mix out of cubase as you have already got the mixes perfect in your control room