ng-zorro-antd/tree-select/style/patch.less

An enterprise-class UI components based on Ant Design and Angular

.ant-tree.ant-select-tree.ant-tree-show-line nz-tree-node:not(:last-child) > li::before {
  content: ' ';
  width: 1px;
  border-left: 1px solid #d9d9d9;
  height: calc(100% - 16px);
  position: absolute;
  left: 12px;
  margin: 26px 0;
}