function toggleTimeline(id, dot) {
  const el = document.getElementById(id);

  if (el.style.display === "none") {
    el.style.display = "block";
    dot.textContent = "";
    dot.classList.remove("collapsed");
  } else {
    el.style.display = "none";
    dot.textContent = "+";
    dot.classList.add("collapsed");
  }
}