So I’ve read most people use the GE add-on switch in 3 way configurations. My dilemma is this:
I have one switch on my wall to the kitchen, which only controls the ceiling lights. I added under cabinet lighting and they are connected to a smartthings/zwave plug (one plug), so I can turn them on and off from my Smartthings app. But would like to add a switch to control the plug.
So simply put, can I use a GE add-on switch to tell the smart plug to turn on the under cabinets lights (essentially adding a “dummy” paddle switch to wirelessly on/off the plug"?
THe GE add-on Switch communicates with its master by a physical “traveler” wire connecting the two switches. As others have mentioned, the GE add on switch does not have its own radio and so it is actually invisible to the smartthings hub. The only thing it can control is the master switch that it is physically wired to.
That said, there are literally dozens of other devices that can work exactly the way you imagined. As long as it has a radio and can communicate directly to the smartthings hub, the switch can send a message to the hub and the hub can send a message to the plug.
Some of these are battery powered, some are mains powered. Some look just like regular wall switches, some look like buttons.
If you want a mains powered dummy switch that does not control a load but that can send a message to the hub, the Linear/GoControl WT00Z is popular. It is designed to create a “virtual three-way” with its master switch, but it can be used in the same way as you describe with anything else that smartthings controls, including the undercabinet lighting plug. It does notuse a physical traveler wire.
To see the others, including the battery powered ones, check the buttons FAQ. This is a clickable link.
So you have the right idea, just the wrong device.