Vue.component('item-list', {
  template: '#item-list-template',
  data() {
    return {
      items: [{
          title: 'item 1'
        },
        {
          title: 'item 2'
        },
        {
          title: 'item 3'
        },
        {
          title: 'item 4'
        },
        {
          title: 'item 5'
        },
        {
          title: 'item 6'
        }
      ],
      activeIndex: -1,
    }
  },
  methods: {
    onItemClick(index) {
      this.activeIndex = this.activeIndex === index ? -1 : index;
    },
    setActiveItemValue(event) {
      const foundItem = this.items[this.activeIndex];
      if (!foundItem) return;
      
      return this.items[this.activeIndex].title = event.currentTarget.value;
    }
  },
  computed: {
    activeItemValue() {
      return this.items[this.activeIndex]?.title ?? '';
    }
  }
});

Vue.component('item', {
  template: '#item-template',
  props: {
    isActive: Boolean,
    title: String
  }
});

new Vue({
  el: '#app'
});

li.active {
  background-color: yellow;
}

<script src="https://cdnjs.cloudflare.com/ajax/libs/vue/2.5.17/vue.js"></script>
<div id="app">
  <item-list></item-list>
</div>

<script type="text/x-template" id="item-list-template">
  <div>
    <input type="text" placeholder="Edit selected items" :value="activeItemValue" @input="setActiveItemValue" />
    <div class="items-col">
      <ul class="items-list">
        <item v-for="(item, i) in items" :key="i" :title="item.title" :isActive="activeIndex === i" @click.native="onItemClick(i)" />
      </ul>
    </div>
  </div>
</script>

<script type="text/x-template" id="item-template">
  <li class="item" :class="{ active: isActive }">{{ title }}</li>
</script>
<style>
    .items-list {
        display: flex;
    }
</style>