library/library_checkout/views/checkout_kanban_assets.xml

<odoo>
    <template id="assets_backend" inherit_id="web.assets_backend"
        name="Library Checkout Kanban Assets">
        <xpath expr="." position="inside">
            <link rel="stylesheet"
                href="/library_checkout/static/src/css/checkout_kanban.css" />
            <script type="text/javascript"
                src="/library_checkout/static/src/js/checkout_kanban.js">
            </script>
        </xpath>
    </template>
</odoo>