fineui/src/css/widget/multitree/multi.css

.bi-multi-tree-combo .multi-select-trigger-icon-button {
  font-size: 16px;
}
.bi-multi-tree-combo .trigger-up {
  display: none;
}
.bi-multi-tree-combo .trigger-down {
  display: block;
}
.bi-multi-tree-combo.combo-show .trigger-up {
  display: block;
}
.bi-multi-tree-combo.combo-show .trigger-down {
  display: none;
}