If you want to control another keyboard from Genos, then use a standard MIDI cable to connect Genos MIDI OUT to the other keyboard MIDI IN
On the Genos MIDI settings page, make sure the panel parts (R1, R2, R3) are assigned to different MIDI channels and have Transmit ON and local control OFF (Otherwise you'll also play the Genos voice)
On the other keyboard MIDI settings, make sure the relevant internal voice parts are set to Receive on the the same MIDI channels as the Genos is outputting.
Finally use standard audio jack cables to connect the other keyboard AUDIO OUT L/R to the Genos AUX IN L/R. Use page 2 of the Mixer (Panel) on the Genos to set the AUX volume properly.
If you then activate say part R1 on the Genos, it should play the voice on the Korg that you assigned to the channel. Same for R2 / R3. You can mix and match whether the part is playing Genos only, Korg only, or even both.
Perhaps you can post a little more detail on what you're struggling with. It is the overall concept, or is something not working.