如图所示，可以实现树状数据的新增子项，新增平级，删除。主要用到了递归

代码：

<template>
  <el-table :data="tableData" style="width: 100%; margin-bottom: 20px" row-key="id" border default-expand-all>
    <el-table-column prop="date" label="Date" />
    <el-table-column prop="name" label="Name" />
    <el-table-column prop="address" label="Address" />
    <el-table-column label="Operations">
      <template #default="scope">
        <el-button size="small" @click="add(scope.row)">新增平级</el-button>
        <el-button size="small" @click="addSon(scope.row)">新增子级</el-button>
        <el-button size="small" type="danger" @click="delItem(scope.row)">删除</el-button>
      </template>
    </el-table-column>
  </el-table>
</template>

<script lang="ts" setup>
import { ref } from 'vue'

const tableData = ref([
  {
    id: 1,
    date: '2016-05-02',
    name: 'wangxiaohu',
    address: 'No. 189, Grove St, Los Angeles',
  },
  {
    id: 2,
    date: '2016-05-04',
    name: 'wangxiaohu',
    address: 'No. 189, Grove St, Los Angeles',
  },
  {
    id: 3,
    date: '2016-05-01',
    name: 'wangxiaohu',
    address: 'No. 189, Grove St, Los Angeles',
    children: [
      {
        id: 31,
        date: '2016-05-01',
        name: 'wangxiaohu',
        address: 'No. 189, Grove St, Los Angeles',
      },
      {
        id: 32,
        date: '2016-05-01',
        name: 'wangxiaohu',
        address: 'No. 189, Grove St, Los Angeles',
      },
    ],
  },
  {
    id: 4,
    date: '2016-05-03',
    name: 'wangxiaohu',
    address: 'No. 189, Grove St, Los Angeles',
  },
])

// 平级新增递归的方法
const addLeaveLoop = (arr: any[], id: number | string) => {
  for (let i = 0; i < arr.length; i++) {
    if (arr[i].id === id) {
      arr.splice(i + 1, 0, { id: +new Date(), date: '2023-11-03', name: '辉辉', address: 'dashjdsakljdl' })
    } else if (arr[i].children) {
      arr[i].children = addLeaveLoop(arr[i].children, id)
    }
  }
  return arr
}
// 新增平级
const add = (row: any) => {
  addLeaveLoop(tableData.value, row.id)
}

// 新增一个子节点的方法
const addSonLoop = (arr: any[], id: number | string) => {
  for (let i = 0; i < arr.length; i++) {
    if (arr[i].id === id) {
      // 判断有没有children，有就前面新增，没有就创建
      if (arr[i].children && arr[i].children.length) {
        arr[i].children.unshift({ id: +new Date(), date: '2023-11-03', name: '张三', address: 'dashjdsakljdl' })
      } else {
        arr[i].children = [{ id: +new Date(), date: '2023-11-03', name: '李四', address: 'dashjdsakljdl' }]
      }
    } else if (arr[i].children) {
      arr[i].children = addSonLoop(arr[i].children, id)
    }
  }
  return arr
}
// 新增子级
const addSon = (row: any) => {
  addSonLoop(tableData.value, row.id)
}

// 删除递归的方法
const delLoop = (arr: any[], id: number | string) => {
  for (let i = 0; i < arr.length; i++) {
    if (arr[i].id === id) {
      arr.splice(i, 1)
    } else if (arr[i].children) {
      arr[i].children = delLoop(arr[i].children, id)
    }
  }
  return arr
}
// 删除
const delItem = (row: any) => {
  delLoop(tableData.value, row.id)
}
</script>