[Vuejs]-How to use optgroup twice inside select tag in a vuejs template in a laravel project?

optgroup has only one level in selects

That means you can insert it only like

<select>
    <optgroup label="1st  label">
        <option> some option </option>
    </optgroup>
    <optgroup label="2st label">
        <option> some option </option>
    </optgroup>
</select>

In alternative ways, you can use the custom select’s packages like Vue Select