Even though there's not one dedicated example, several others have got preselected value, f.e. colour variations:

<template>
  <mdb-container>
    <mdb-select
      color="primary"
      v-model="colorOptions"
      label="Blue select"
    />
  </mdb-container>
</template>
<script>
  import { mdbSelect, mdbContainer } from "mdbvue";
  export default {
    name: "SelectPage",
    components: {
      mdbSelect,
      mdbContainer
    },
    data() {
      return {
        colorOptions: [
          { text: "Option nr 1", value: "Option 1", selected: true },
          { text: "Option nr 2", value: "Option 2" },
          { text: "Option nr 3", value: "Option 3" },
          { text: "Option nr 4", value: "Option 4" },
          { text: "Option nr 5", value: "Option 5" }
        ]
      };
    }
  };
</script>

Works the same for the multiselect. Thank you for your remarks, we will provide this example in our documentation in the nearest future. Kind regards, Magdalena