AppleScriptに比べると面倒くさいけど直接キーボードイベントを発火させる方法もあるよ

//Cmd+Tabキーの例
let tab_down = CGEvent(keyboardEventSource: nil, virtualKey: 0x30, keyDown: true)
let tab_up = CGEvent(keyboardEventSource: nil, virtualKey: 0x30, keyDown: false)
tab_down?.flags = CGEventFlags.maskCommand
tab_up?.flags = CGEventFlags.maskCommand
tab_down?.post(tap: CGEventTapLocation.cghidEventTap)
tab_up?.post(tap: CGEventTapLocation.cghidEventTap)