I'm afraid there is no out of the box solution. The only thing I can think of is postprocess-article-html-fn, see http://cryogenweb.org/docs/customizing-cryogen.html#post-process-article-content-with-selmer You might want to make a fork of the Markdown plugin??? Because that's is the one producing the html...

Look at https://github.com/vsch/flexmark-java allows...

It supports "Custom node rendering API with ability to invoke standard rendering for an overridden node, allowing custom node renders that only handle special cases and let the rest be rendered as usual." it seems...

This is really useful, thanks. Do you know if it Is any easier if I switch to asciidoc instead of markdown?

Not sure, really. For markdown, see this https://github.com/vsch/flexmark-java/blob/master/flexmark-java-samples/src/com/vladsch/flexmark/java/samples/NodeRendererSample2.java

It seems asciidoctor supports custom templates, I guess that works help, see https://docs.asciidoctor.org/asciidoctorj/latest/asciidoctor-api-options/#templatedirs Personally I think asciidoctor is thousand times better that md for writing about code. Ymmv More about asciidoctor templates and link to examples https://docs.asciidoctor.org/asciidoctor/latest/api/load-templates/ > Asciidoctor will use the templates in this directory instead of its built-in templates for any elements for which it finds a matching template.

Yes, Asciidoc looks much more suitable. I am not sure if I understand the templates. They seem a very different syntac to Custom coverters, which seem a lot clearer way of overriding the built-in html5 converter output This commenthttps://github.com/asciidoctor/asciidoctor/issues/2273#issuecomment-475846369 I can over-ride the built-in converters for html5 and create my own custom html output, which sounds ideal.

class Html5ConverterBulma < (Asciidoctor::Converter.for 'html5')
 register_for 'html5'
  def convert_paragraph h3
  %(<h3 id="TODO:how-to-create-an-id" class="title is-4 is-spaced bd-anchor-title" basic-navbar="">
    <span class="bd-anchor-name">#{h3.content}</span>
      <a class="bd-anchor-link" href="#basic-navbar">#</a></h3>)
   end   
end

No idea. Regarding the templates - I would ask https://discuss.asciidoctor.org/ where the built in ones and how to write custom ones if it is unclear. Perhaps they could improve the docs....

Hmm, there is a nice asciidoc mode in Emacs (Spacemacs) so thats an added bonus 🙂 I will continue to investigate, as a few custom converters are the missing piece I need to create an interactive and responsive website for my books with Cryogen The books will look similar to the http://bulma.io website (with different content of course)