Ah amazing thank you! I pulled the latest and reloaded GMEdit and it works great.
I did initially try the "reload" link for the plugin in Preferences, but it just brings up a blank white window and nothing happens. Might be an Electron problem?
One thing I did notice is I cannot close the Aside that comes up (via Peek Aside) after creating the script, as there is no Hide Aside option in the right-click menu as there usually is. Worked around it by closing the tab for the script. Normal Asides can be hidden fine.