I tested some workarounds for canvas.
It is very convenient to use assets for that. Edit a htm file with an external html editor. Save it wit the html suffix.
Then load this file in your project. If your editor did not use the suffix html, you simply rename the uploaded file.
With the webviewer you can load your file (simply the filename with html suffix).
This seems to me very easy. The sideeffect is, that you can publish your html file as plain text in this forum.
I am now testing with canvas that fits to the screen and drawing with fingertouch. When ready, I will publish.
By the way: I would like to have a vety simple text editor in the thncable x environment, because then it would be easier to make changes…