通过伪元素，实现这个和step长得差不多的样式

<template>
  <el-select
    v-model="value"
    placeholder="请选择提报单位"
    style="width: 430px"
  >
    <el-option
      v-for="(item, i) in officeList"
      :class="'el-option ' + getClass(i)"
      :key="item.value"
      :label="item.label"
      :value="item.value"
    >
    </el-option>
  </el-select>
</template>

<script>
export default {
  data() {
    return {
      value: "",
      officeList: [],
    };
  },
  created() {
    this.officeList = [
      {
        value: "选项1",
        label: "黄金糕",
      },
      {
        value: "选项2",
        label: "双皮奶",
      },
      {
        value: "选项3",
        label: "蚵仔煎",
      },
      {
        value: "选项4",
        label: "龙须面",
      },
      {
        value: "选项5",
        label: "北京烤鸭",
      },
    ];
  },
  methods: {
    // 获取当前行的样式
    getClass(i) {
      if (i === 0) {
        if (this.officeList.length > 1) return "el-option-start";
        else return "";
      } else if (i === this.officeList.length - 1) {
        return "el-option-end";
      } else {
        return "el-option-center";
      }
    },
  },
};
</script>

<style lang="scss" scoped>
.el-option {
  width: 430px;
  --round-color: #bebfc2;
}
.el-option:hover {
  color: #1e7e73;
  font-weight: 600;
  background-color: #e9f7f7;
  --round-color: #1e7e73;
}
.el-option-start::before {
  content: "";
  position: absolute;
  top: 50%;
  left: 10px;
  height: 50%;
  border-left: 1px dashed var(--round-color);
}
.el-option-center::before {
  content: "";
  position: absolute;
  top: 0;
  left: 10px;
  height: 100%;
  border-left: 1px dashed var(--round-color);
}
.el-option-end::before {
  content: "";
  position: absolute;
  top: 0;
  left: 10px;
  height: 50%;
  border-left: 1px dashed var(--round-color);
}
.el-option::after {
  content: "";
  position: absolute;
  top: 50%;
  left: 10px;
  transform: translate(-40%, -50%);
  width: 8px;
  height: 8px;
  border-radius: 50%;
  border: 1px solid var(--round-color);
  background: #fff;
}
</style>