It would be nice if the Markdown backend would ship multiple CSS files so that the user can change the style how the Markdown code is rendered. The style should be changed via "Settings -> Configure Backends -> Markdown". A lot of Markdown editors (e.g. Haroopad) already ship different CSS styles (e.g. "Solarized Light/Dark" and so on).
I agree. See also https://bugs.kde.org/show_bug.cgi?id=426682.
I support this request, along with support for custom user CSS.