highlighting markdown mark only?

v6
3

This is how it’s done:

import { markdown, markdownLanguage } from '@codemirror/lang-markdown'
import { languages } from '@codemirror/language-data'
import { EditorState } from '@codemirror/state'
import { MarkdownConfig } from '@lezer/markdown';

const customTags = {
  headingMark: Tag.define(),
};

const MarkStylingExtension: MarkdownConfig = {
  props: [
    styleTags({
      HeadingMark: customTags.headingMark,
    }),
  ],
};

const highlightStyle = HighlightStyle.define([
 {
    tag: customTags.headerMark,
    color: 'blue',
  },
  {
    tag: tags.heading1,
    color: 'black',
    fontSize: '1.75em',
    fontWeight: '700',
  },
]);

const editorState = EditorState.create({
  doc: options.doc,
  selection: options.selection,
  extensions: [
    markdown({
      base: markdownLanguage,
      codeLanguages: languages,
      extensions: [MarkStylingExtension],
    }),
   highlightStyle,
  ],
});

You can find the other names like HeadingMark in the @lezer/markdown package, around here.