design-themes/theme_enark/views/customize_modal.xml

<?xml version="1.0" encoding="utf-8"?>
<odoo>
    <template id="theme_customize" inherit_id="website.theme_customize">
        <!-- Set number of fonts -->
        <xpath expr="//t[@t-set='_nb_fonts']" position="attributes">
            <attribute name="t-value">11</attribute>
        </xpath>
    </template>
</odoo>