Lack of interest Add <optgroup> to Drop down selection in Custom thread fields

[NHATKYMUA]

It would be really awesome if we would be able to add <optgroup> to Drop down selection in Custom thread fields

<select>
  <optgroup label="Swedish Cars">
    <option value="volvo">Volvo</option>
    <option value="saab">Saab</option>
  </optgroup>
  <optgroup label="German Cars">
    <option value="mercedes">Mercedes</option>
    <option value="audi">Audi</option>
  </optgroup>
</select>