The add-on switches cannot be used to trigger scenes. It’s hard to find information on this, but here’s one post where I did:
(I’m guessing this makes them useless in relay-disables scenarios as you might do with smart bulbs, so they’re probably only good if you want on/off control of a switched, multi-way load. FWIW, they can work with scenes on a HomeSeer switch, or at least HomeSeer’s can and I assume GE’s would work the same.)