.sidebar-nav li.sidebar-folder > ul {
  display: none;
}

.sidebar-nav li.sidebar-folder.open > ul {
  display: block;
}

.sidebar-nav li.sidebar-folder > strong,
.sidebar-nav li.sidebar-folder > p > strong {
  cursor: pointer;
  user-select: none;
}

.sidebar-nav li.sidebar-folder > strong::before,
.sidebar-nav li.sidebar-folder > p > strong::before {
  content: '▸';
  display: inline-block;
  width: 1em;
}

.sidebar-nav li.sidebar-folder.open > strong::before,
.sidebar-nav li.sidebar-folder.open > p > strong::before {
  content: '▾';
}