This bug is from the fCPU. Fix it if possible.
The window with the code is oriented by the width of the combinator window itself. Therefore, part of the text (right edge) is not visible at all. Also the selection works only up to a certain part. That is, we cannot select the outermost few characters. Clicking does not work there.

https://youtu.be/r7DrCPStaMU

you can set the width of the editor from the player options
The lua api is somewhat limited in terms of text, anyway I will check if it can be improved

https://imgur.com/rx7dkuB

I set the width of the code editor to 800 points, but nothing has changed. Specifically here is the problem:
Red text - to where it shows up. The blue line - to where it is hidden and where our cursor can be located to write (we can not see it. Also seen in the video).
The black line - in theory, the area up to where the text should be.
And by the way, can you add a horizontal slider? It would be more convenient, I think.

Ok, now I understand the problem better. I add it to the TODO list to correct it

Fixed in version 0.5.0