DJM 450 CUE of AUX IN and USB send/return

Hi There

I just bought a new djm 450 and I am happy with most of the functions. I work with tractor 4 and use the internal soundcard.
As I want to use it as a 3-channel mixer with use of AUX IN, I wonder if there is a way to pre listen the AUX IN with volume knob down. It’s absolutely a need to pre-listen to my extra channel before I fade it in.

I tried to solve it with USB send/return function and was disappointed to read that this function is only working with ipad. I don’t understand why this function cannot be used just with the normal built-in channels. I guess for most users it would be more beneficial in this way. Because having an ipad beside my laptop does not make sense to me.

However, I am still looking for a solution to my AUX In CUE problem and I will be grateful for any advice.

Thanks.