Ok, let’s take it from the top now that we have the wiring configuration down.
This is a neutral installation with the Inovelli in the box with the multiple Romex.
I recommend that you do this in two stages. I think you might already have the first one in place, but wire the Inovelli in the multi-Romex box as a 2-way. Make sure that’s working ok, then add in the Aux.
In the multi-Romex box, the two 2-wires at the top left are the line in and downstream, so both blacks the the line terminal. Bundle the whites EXCEPT the white of the 3-wire going to the other switch. Add a white pigtail to that bundle and connect that to the neutral terminal on the Inovelli, leaving the other neutral hole open. Connect the black of the 2-wire, top right (the load going to the light) to the Load terminal.
That should configure the switch as a 2-way switch and work to turn on and off and dim the light.
Once that is working properly, add the Aux to the other box. In the multi-Romex box and the 3-wire going to the other box, red to Inovelli Traveler and white to the 2nd hole on the Inovelli Neutral. Cap off the black as it’s not used.
At the other switch box with the Aux, red to Traveler, white to Neutral, cap off the black. Adjust the switch settings to reflect you are using an Aux.
That should be it!