Oml thank you for the undo/redo lol. I was losing my mind over it. If you havent already please make it so I can click and drag text, and pasting text doesn't seem to work, which would be nice to have. Lastly, I think you should have Script tabs, similar to the ones in Pico-8, but perhaps they are on the left side of the code editor. I am fine editing with one big script in my IDE but I think others would really like this idea.
Currently there still isn't mouse selection for text (or selection for text in general), but I will try to work this in. Pasting text was broken for Unicode or extended ASCII but should now be fixed -- although non-ASCII characters are rendered as the "sad box". I haven't considered script tabs, but I have considered the possibility of adding indent-based code folding.