this.$refs.viewTree.setCurrentKey(node_id); //"viewTree"是你自己在樹形控制元件上設定的 ref="viewTree"

<el-tree
        ref="viewTree"
        :default-expanded-keys="['控制元件', '模板']"
        node-key="id"
        :highlight-current="highlight_current"
        :data="tree_data"
        class="tree" 
        :props="defaultProps" 
        @node-click="handleNodeClick"
        style='margin-bottom: 20px'
        >
        </el-tree>
 

<script >
    export default{
        data(){
            return {
                tree_data: [{
                id: 'l1_1',
                label: '一級節點1',
                children: [{
                  label: '節點1-1',
                  id: 'l1_1_1',
                }, {
                  label: '節點1-2',
                  id: 'l1_1_2',
                }, {
                  
                  label: '節點1-3',
                  id: 'l1_1_3',
                }]
              }, {
                label: '一級節點2',
                id: 'l1_2',
                children: [{
                  label: '節點2-1',
                  id: 'l1_2_1',
                }]
              }],
            }
        }
    }
</script>
 

node_id可以是tree_data中的任何一個節點的id