vue-select/docs/components/SlotSelectedOption.vue

<template>
  <v-select v-model="selected" :options="books" label="title">
    <template #selected-option="{ title, author }">
      <div style="display: flex; align-items: baseline;">
      <strong>{{ title }}</strong>
      <em style="margin-left: .5rem;">by {{ author.firstName }} {{ author.lastName }}</em>
      </div>
    </template>
  </v-select>
</template>

<script>
const book = {
  title: "Old Man's War",
  author: {
    firstName: "John",
    lastName: "Scalzi"
  }
};
export default {
  data: () => ({
    books: [book],
    selected: book
  })
}
</script>