struct ContentView: View {
   @Environment(\.openWindow) var openWindow

   var body: some View {
      VStack {
         Text("Hello, world!")
         Button("Open Auxiliary Window") {
            openWindow(id: "mywindow")
         }.buttonStyle(.borderedProminent)
      }
      .frame(minWidth: 500, maxWidth: .infinity, minHeight: 300, maxHeight: .infinity)
    }
}