Hi,
I had the same problem and contacted the Steinberg support in Germany. I got the following answer (I translated it):
Unfortunately, it is not possible to put the DAW Signal on another Mix. This function hasn’t been designed/provided in the DSP Mixer on the digital platform.
Still, you can combine Analog Out 1/2 with Analog In 3/4. Then, mute channels 3/4 in Mix 1 in order to avoid doubling the signal.
In Mix 2, Mix 3 and Mix 4 you will now have the DAW signal on channels 3/4.
There is no other way to get around this problem
I must say that I am very surprised by this answer. Why is there a DAW Fader in Mix 2-4 if it is of no use?? To have the DAW on each Mix is one of the very basic features one needs when it comes to monitor mixes in the studio, so why did nobody at Steinberg think about this when they designed the digital platform? The solution that the support suggests will have the effect that two inputs are missing, which isn’t really satisfying.
I am disappointed by Steinberg.