Header numbering for Confluence Pages. Use the HTML macro to implement. You can put this CSS into your theme, individual pages or use it in templates.

confluence-header-numbering.css

/*
 * This is an opionionated chunk of CSS.
 * It add's numbering to headers h2 and h3.
 * 
 * Why not for h1? h1 is the page title.
 * Why not for h4? Because that's to deep.
 *
 * Adapt as needed :-)
*/

.contentLayout2 {
  counter-reset: h2 h3;
}

.innerCell > h2 {
  counter-reset: h3;
}

.innerCell > h2::before {
  content: counters(h2, ".") " ";
  counter-increment: h2;
}

h3::before {
  content: counter(h2) "." counter(h3) " ";
  counter-increment: h3;
}