Just wanted to add you don’t have to link/unlink in the Alexa app every time you add a device in order to get Echo to see it. In SmartThings App, you should have an Amazon Echo SmartApp after the initial link where your new device (physical or virtual switch) can be selected. At that point a discover devices either via app or voice should find it. See JD’s FAQ, while the app screenshots are a little out of date information is still good.