una/template/form_field_nested_form_wrapper.html

<div id="bx-nested-form-{nested_type}-{item_id}" class="bx-nested-form-ghost bx-def-margin bx-def-padding bx-def-border bx-clearfix">
    <div class="bx-nested-form-ghost-form">
        __nested_form__ 
        <div class="bx-nested-form-actions bx-def-margin-top bx-clearfix"><a class="bx-btn bx-btn-small" href="javascript:void(0);" onclick="{js_instance_name}.deleteGhost(this, '{nested_type}')"><bx_text:_sys_form_input_nested_form_button_delete_item /></a></div>
    </div>
</div>