fastapi-admin/fastapi_admin/templates/widgets/inputs/many_to_many.html

{% with id = 'form-select-' + name %}
    <div class="form-group mb-3">
        <div class="form-label">{{ label }}</div>
        <select multiple class="form-select" name="{{ name }}" id="{{ id }}">
        </select>
        {% if help_text %}
            <small class="form-hint">
                {{ help_text }}
            </small>
        {% endif %}
    </div>
    <script>
        new Choices(el = document.getElementById('{{ id }}'), {
            classNames: {
                containerInner: el.className,
                listDropdown: 'dropdown-menu',
                itemChoice: 'dropdown-item',
                activeState: 'show',
                selectedState: 'active',
                inputCloned: 'bg-white',
            },
            removeItemButton: true,
            choices:{{ options|safe }}
        });
    </script>
{% endwith %}