As long as all the switches are controllable by SmartThings, that’s all you need. Switch A will talk to the hub and then the hub will send a message to the other three switches.
You will hear some people talk about “Z wave direct association.” That’s a feature that works only between Z wave switches, and only some zwave switches. You need the trigger switch, but in this case that’s all 4 switches, to support that kind of association.
But these days, I do not recommend people use direct association, they almost Always end up unhappy.
Zwave Direct association was invented before people used smart phones much, and the way it works is that the trigger switch is given permission to talk directly to the target switch without telling the hub about it.
The problem with that is it then your mobile app won’t necessarily know that the switches were turned on and it becomes much harder to set up other rules depending on the switches going on and off. You might save 3/4 of a second in lag, but you will spend a lot more time than that trying to figure out what exactly the statuses of everything.
Zwave Direct association also cannot be controlled with rules or time of day or day of the week or anything else. It just happens bang bang every time. And there might be times when you want to turn off the lights on the staircase without turning off the light downstairs. Or Only light one section of the basement.
Direct association is an old technology that was suited to an older lifestyle. If you already have a bunch of Zwave classic devices (that’s the older generation), then, sure, it may be your best option. But if you’re starting out new with zwave plus devices, there are other, better options now.
The primary replacement for it is “central scenes” And many of the newest (2016 or newer models) zwave switches support that. (Note that the word “scenes” is used in many different ways in home automation. So we are not talking about smartthings scenes or Z wave local scenes or hue scenes. Just specifically “zwave central scenes“)
With the central scene, the switch sends a message to the hub and then the hub sends messages to the other devices in the scene based on rules that you have created. So that means you can put all kinds of restrictions and “if A unless B” And all that. And the hub knows what happens, so the hub and the app are always up-to-date on the statuses of all devices.
I’m not 100% opposed to zwave direct association. Its biggest advantage is that it will work even if your hub dies completely. So if you had a switch at the top of the attic stairs and one at the bottom, I might use zwave direct association for that. Most of the time you aren’t going up into the attic anyway, so it’s unlikely you’re going to want to put other fancy rules around it. And it’s a good safety feature to make sure they always work.
But most of the time I think people prefer the accuracy and flexibility of central scenes.