MINI

C:/xampp/phpMyAdmin/templates/display/export/

files >> C:/xampp/phpMyAdmin/templates/display/export/select_options.twig

 <div>
    <p>
        <a href="#" onclick="Functions.setSelectOptions('dump', 'db_select[]', true); return false;">
            {% trans 'Select all' %}
        </a>
        /
        <a href="#" onclick="Functions.setSelectOptions('dump', 'db_select[]', false); return false;">
            {% trans 'Unselect all' %}
        </a>
    </p>

    <select name="db_select[]" id="db_select" size="10" multiple>
        {% for database in databases %}
            <option value="{{ database.name }}"{{ database.is_selected ? ' selected' }}>
                {{ database.name }}
            </option>
        {% endfor %}
    </select>
</div>