.rc-category-tree .children {
  display: none;
  margin-left: 1em;
  list-style: none;
}

.rc-toggle-icon {
  cursor: pointer;
  display: inline-block;
  width: 1em;
}
.rc-toggle-icon.no-children {
  visibility: hidden;  /* hide icon for leaf nodes */
}
.rc-toggle-icon.open {
  transform: rotate(90deg);  /* or swap to “▼” */
}