Looking for a virtual switch(three way switch hack)

I’m not quite following the question. What do you mean by “be a virtual switch/button triggered by a switch?”

If you are asking if you can toggle a conventional dumb switch and have it in some way send a signal to the smartthings hub, then the usual answer is a micro. You have to connect some radio to the dumb switch. But that’s a physical device, not a virtual one. You can’t use a virtual device to add radio capability to a dumb switch.

It’s possible to just use a networked contact sensor with dry contacts, but you absolutely should not put a battery operated device inside the wall. It’s a fire hazard.

Some people have created a button push device that sits on top of the wall using such a sensor, but it doesn’t sound like that’s what you want.

If you want to take an existing dumb switch and have it communicate to the smartthings hub, then, yes, connect it to an in wall micro. That’s the device class designed for this purpose, whether it controls an actual load or not.

If it doesn’t control the load, though, you have to know what you’re doing with the wiring.

And I know the following is not what you yourself are looking for, but since there may be other people in the forums to come across this thread looking for something a bit different, here’s the list of buttons and remotes that work with SmartThings. Some of them look just like wall switches. But I do understand that you yourself don’t want to replace your existing wall switch.