Now to discuss auxiliary switches.
(I’m too tired to go into the technical details, but let’s not talk about “scene controllers.” That has a very specific technical meaning within Z wave, and it’s not what you need in a SmartThings environment for what you’re describing. So just don’t worry about those at all. You just need an auxiliary switch.)
OK, there are three ways by which an auxiliary can communicate to the master.
1) physical traveler wire. This is how GE and a few other models do it.
In this case, the auxiliary will be invisible to the smart things hub. It typically, as in the case of GE, doesn’t even have a radio. It normally needs to be on the same neutral as the master.
Two) wirelessly from the auxiliary to the master without telling the hub what happened. This is how the Leviton Vizia plus series is designed to work. It’s also how the Coopers are designed to work if you use direct association with them. These can be Mains powered auxiliaries or battery powered, but in any case they are not load control switches. The ones that are mains powered do need to have power and are typically designed to use a neutral to power their radios. They will show up on your things list. Note that these will need to be within one hop of each other, typically within the same room. And they both need to be Z wave switches that can use association.
( this is where the Z wave “scene controllers” would go but we don’t want to use those with SmartThings because although they can control another Z wave device in the same room, they will not tell SmartThings about any button presses and so you’re really limited in what you can use them for as compared to just a regular zwave auxiliary switch.)
Three) wirelessly from the auxiliary to the hub and then from the hub to the master. Or to any other device. This is commonly how a wall switch controls a smart bulb even if they are of different protocols.
If you go with this option you can add as many devices as you want and you can mix-and-match them however you want because since they are not loadbearing it doesn’t matter what circuits the mains powered ones are on. Each one is just seen as an individual device to SmartThings.
The Linear/GoControl zwave auxiliary switch, the WT00Z model, is popular for this purpose if you don’t need a battery operated one. It looks just like a regular switch except it does not control the load. You don’t have to have a master switch to go with it because it will pair with smartthings as a Z wave switch.
If you want a battery-operated one, the cooper aspire 9500 is popular as it looks the most like a regular wall switch. But a lot of people prefer to go with the button types like the remotec.
You’ll find both of these and more battery operated devices in the buttons FAQ: