org-html-theme-darksun VS github-markdown-css

Yeah, that's Solarized Dark using https://github.com/alphapapa/org-html-theme-darksun. Looking at your site, I'm thinking that I ought to do a Solarized Light version too. The handbook is also viewable on GitHub, which may be more readable in some ways: https://github.com/alphapapa/emacs-package-dev-handbook

It's certainly possible, more a question of implementing it. There are a few org export themes that implement folding, like this one: https://github.com/alphapapa/org-html-theme-darksun.

And I know the famous alphapapa has one they use here. Does that help?

Nowadays, most application documentation is moved onto a website, which forces users to switch to a web browser every time they want to read some basic documentation. Furthermore, docs on the web can become quite convoluted, resulting in additional times spent just looking for the right section. But as it turns out, using the JavaFX WebView, Flexmark, AtlantaFX Popovers, and for example GitHub Markdown CSS, you can achieve a fancy markdown display within your application at exactly the place you want:

You can download a GitHub Markdown CSS and then I think use it as the Custom CSS in MarkdownPad.

sindresorhus/github-markdown-css - The minimal amount of CSS to replicate the GitHub Markdown style

github-markdown-css

I'd say if you can't find what you like just make something. I found this https://github.com/sindresorhus/github-markdown-css, maybe that can be a starting point? Good luck!