You can use a remote terminal application on your Android device such as Termux or cygwin/wsl2 on Windows for hotkey/programmatic library switching, or you can enter the MCWS url in a browser (save in a bookmark for easy access) if that is more of your style. If you are doing this from your WAN you'll probably want to enable SSL, so just sub in your host IP and the integer that corresponds to your library:
https://host.ip:52200/MCWS/v1/Control/MCC?Command=20025,1
...and visit that address in your remote browser.