partner-contact/partner_multi_relation_tabs/views/menu.xml

<?xml version="1.0" encoding="UTF-8"?>
<odoo>

        <act_window
            id="action_res_partner_tab"
            res_model="res.partner.tab"
            view_mode="tree,form"
            name="Relation Tabs"
        />

        <menuitem
            id="menu_res_partner_tab"
            parent="partner_multi_relation.menu_res_partner_relation"
            action="action_res_partner_tab"
            sequence="80"
        />

</odoo>