<div class="spc-wrapper">
    <select name="{{widget.name}}" id="{{widget.attrs.id}}" class="spc-select">
        {% for k,v  in choices %}
        <option value="{{k}}">{{v}}</option>
        {% endfor %}
        <option value="CUSTOM">Custom - Enter below</option>
    </select>
    <input type="text" name="custom-{{widget.name}}" maxlength="{{widget.attrs.maxlength}}" class="spc-custom">
</div>

Add select + custom widget
Add select + custom widget
