.sidebar-nav li {
  position: relative;
  margin: 0;
  cursor: pointer;
}
.sidebar-nav ul:not(.app-sub-sidebar) > li:not(.file)::before {
  content: "";
  display: block;
  position: absolute;
  top: 5px;
  left: -12px;
  height: 6px;
  width: 6px;
  border-right: 1px solid #505d6b;
  border-bottom: 1px solid #505d6b;
  transform: rotate(-45deg);
  transition: transform 0.1s;
}
.sidebar-nav ul:not(.app-sub-sidebar) > li.open::before {
  transform: rotate(45deg);
}
.sidebar-nav ul:not(.app-sub-sidebar) > li.collapse::before {
  transform: rotate(-45deg);
}