Here’s the FAQ on how to create a virtual switch:
Once you have one, it works like any other switch. You can authorize IFTTT or Harmony to access it. You can link it to other lights/switches through The Big Switch smartapp. Or you can use it to trigger Hello Home Actions through the community-created Big Switch for Hello Home Actions. Or access it through other custom Smartapps, including the community-created rules engines.
Harmony will think it’s just a switch, and you can assign it to one of the remote’s home automation buttons or include it in a harmony action. Once it’s turned on or off, it will be up to the scheduling you’ve set up on the SmartThings side to make things happen.