I had a thought- the reason that it isn’t working with notepad is that it doesn’t seem to handle certain text characters very well- try installing notepad++ and see if that makes a difference in creating scripts.

As far as stella goes, you can type stella into the terminal and it will open stella or you can change your default emulator by pressing x or m as a rom loads and change it from libretro to stella. If you are are trying to exit emulationstation, if you press a button after you exit emulationstation it will allow you to go into the terminal. if you don’t press anything it will just reboot back into emulationstation.