una/studio/template/agents_agents_form_input_select.html

<div id="bx-agents-agents-form-input-cont" style="overflow:visible;">
    <select id="bx-agents-agents-form-input" name="form_input" class="bx-def-font-inputs bx-form-input-select">
        <bx_repeat:form_inputs>
            <option value="__value__" <bx_if:sel>__sel__</bx_if:sel> data-title="__title_attr__" data-form_input="__value__">__title__</option>
        </bx_repeat:form_inputs>
    </select>
    </div>
    <script>        
        $('#bx-agents-agents-form-input').select2({
            templateResult: (state) => {
                return $(`
                    <div class="bx-form-input-wrap">
                    <div>
                        <div class="bx-form-input-data">${state.text || state.id}</div>
                    </div>
                    </div>
                `);
            },
            templateSelection: d => d.text,
            tags: true, // allow custom inputs
            createTag: function (params) {            
                const term = $.trim(params.term);
                if (!term) return null;
                return {
                    id: term,
                    text: term,
                    title: term,
                    title_attr: term,
                    value: term,
                };
            },
            placeholder: "Select or type a value"
        });    
    
    </script>