quartz/assets/js/code-title.js

function addTitleToCodeBlocks() {
  const els = document.getElementsByClassName("highlight");
  for (let i = 0; i < els.length; i++) {
    try {
      if (els[i].title.length) {
        let div = document.createElement("div");
        if (els[i].getElementsByClassName("code-title").length) continue;
        div.textContent = els[i].title;
        div.classList.add("code-title")
        els[i].insertBefore(div, els[i].firstChild);
      }
    } catch (error) {
      console.debug(error);
    }
  }
}