I think the closest thing in the modern world is probably side-by-side editors for things like Markdown and LaTeX, eg: https://www.xm1math.net/texmaker/ https:

I think the closest thing in the modern world is probably side-by-side editors for things like Markdown and LaTeX, eg: https://www.xm1math.net/texmaker/ https://www.xm1math.net/texmaker/