2 different area lights, single hot wire

Please help me understand how this wiring works. For 2 areas, stairs and hallway, I’d like to replace current 3-way dumb switches with Inovelli LZW30-SN & GE Enbrighten Add-On (46199) switches in each area.

After disconnecting switches and testing all wires for power, there’s only a single hot wire (for the hallway). Stair lights appear to get power from having it’s white wire twisted with hallway black wire. See images.

How can I wire in the LZW30-SN and Enbrighton add-on switch?

Here’s what appears to be happening:

The stairs seem to be a load/line in the same box, and the hallway appears to be load/line in separate boxes. (Don’t trust me. Be sure to verify this.)

I haven’t personally used AUXes, so I don’t know the wiring off the top of my head. When looking at the Inovelli wiring diagrams, be aware that wire colors may not match what you are using. What matters is the function of each wire.

Not sure if you already figured this out. Based on your narrative and some educated guessing here is what I think would work. I’m assuming you have a neutral in the 3 way box you’re not showing, I think the add-on switch requires it. If you don’t, you can wire the existing white wire acting as a hot to the neutral bundle in the dual gang box. I’m also assuming the wiring diagram above is correct (it would be my guess as well based on the same information).

In the dual gang box, the white wire is currently a hot wire, replace that with a pigtail to the line of the switch. The black wire on its own is likely the load. The red wire would go to the traveler. You need a neutral I believe that you can use a pigtail from the existing neutral bundle. You will be abandoning the black and white wire going to the other box (unless you need to reuse the white to get a neutral into the other box)

I’m the aux switch position you hook up just the red wire and the neutral. Abandon the white and black wire entirely (same not as above).