moodle_theme_ilb/templates/core/url_select.mustache

<div class="{{classes}}">
    <form method="post" action="{{action}}" class="form-inline" id="{{formid}}">
        <input type="hidden" name="sesskey" value="{{sesskey}}">
        <div class="form-group">
            {{#label}}
                <label for="{{id}}" {{#labelattributes}}{{name}}="{{value}}" {{/labelattributes}}>
                    {{label}}
                </label>
            {{/label}}
            {{#helpicon}}
                {{>core/help_icon}}
            {{/helpicon}}
            <select {{#attributes}}{{name}}="{{value}}" {{/attributes}} id="{{id}}" class="custom-select {{classes}}" name="jump">
                {{#options}}
                    {{#isgroup}}
                        <optgroup label="{{name}}">
                            {{#options}}
                                <option value="{{value}}" {{#selected}}selected{{/selected}}>{{name}}</option>
                            {{/options}}
                        </optgroup>
                    {{/isgroup}}
                    {{^isgroup}}
                        <option value="{{value}}" {{#selected}}selected{{/selected}}>{{name}}</option>
                    {{/isgroup}}
                {{/options}}
            </select>
        </div>
        {{#showbutton}}
            <input type="submit" class="btn btn-secondary" value="{{showbutton}}">
        {{/showbutton}}
        {{^showbutton}}
            <noscript>
                <input type="submit" class="btn btn-secondary" value="{{#str}}go, core{{/str}}">
            </noscript>
        {{/showbutton}}
    </form>
</div>