partner-contact/base_location_nuts/views/res_partner_view.xml

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

<record model="ir.ui.view" id="view_partner_form_nuts">
    <field name="name">Partner form with NUTS</field>
    <field name="model">res.partner</field>
    <field name="inherit_id" ref="base.view_partner_form"/>
    <field name="arch" type="xml">
        <xpath expr="//sheet/group//field[@name='country_id']/.." position="after">
            <field name="nuts1_id"/>
            <field name="nuts2_id"/>
            <field name="nuts3_id"/>
            <field name="nuts4_id"/>
        </xpath>
        <xpath expr="//field[@name='child_ids']/form//field[@name='country_id']/.." position="after">
            <field name="nuts1_id"/>
            <field name="nuts2_id"/>
            <field name="nuts3_id"/>
            <field name="nuts4_id"/>
        </xpath>
    </field>
</record>

<record model="ir.ui.view" id="view_res_partner_filter_nuts">
    <field name="name">Partner search with NUTS</field>
    <field name="model">res.partner</field>
    <field name="inherit_id" ref="base.view_res_partner_filter"/>
    <field name="arch" type="xml">
        <field name="category_id" position="after">
            <field name="nuts1_id"/>
            <field name="nuts2_id"/>
            <field name="nuts3_id"/>
            <field name="nuts4_id"/>
        </field>
        <filter name="salesperson" position="after">
            <filter string="NUTS L1"
                    domain="[]"
                    context="{'group_by': 'nuts1_id'}"/>
            <filter string="NUTS L2"
                    domain="[]"
                    context="{'group_by': 'nuts2_id'}"/>
            <filter string="NUTS L3"
                    domain="[]"
                    context="{'group_by': 'nuts3_id'}"/>
            <filter string="NUTS L4"
                    domain="[]"
                    context="{'group_by': 'nuts4_id'}"/>
        </filter>
    </field>
</record>

</odoo>