Using Inheritance Add a smart button with an action to view a list of one2many or many2many records

partner_orders_smart_button.py

class Customer(models.Model):
    _inherit = "res.partner"

    orders = fields.One2many('sale.order', 'partner_id', string="Orders")
    orders_count = fields.Integer(compute='_orders_count', string="Orders Count",store=True)
    
    @api.depends("orders")
    def _orders_count(self):
        for rel in self:
            count_id = self.env['sale.order'].search_count([('partner_id', '=', rel.id)])
            rel.orders_count = count_id
            
    def button_action_orders(self):
        return {
            'name': 'Orders',
            'type': 'ir.actions.act_window',
            'domain': [('partner_id', '=', self.id)],
            'view_type': 'form',
            'view_mode': 'tree,form',
            'res_model': 'sale.order',
            'view_id': False,
            'views': [(self.env.ref('sale.view_order_tree').id, 'tree'),
                      (self.env.ref('sale.view_order_form').id, 'form')],
            'target': 'current',
        }

partner_orders_smart_button.xml

<odoo>
  <data>
    <record id="res_partner_form_inherit" model="ir.ui.view">
        <field name="name">res.partner.form.inherit</field>
        <field name="model">res.partner</field>
        <field name="inherit_id" ref="base.view_partner_form"/>
        <field name="priority" eval="8"/>
        <field name="arch" type="xml">
            <xpath expr="//form/sheet/div[@class='oe_button_box']" position="inside">
                <button name="button_action_orders" type="object" class="oe_stat_button" icon="fa-exchange">
                    <field name="orders_count" widget="statinfo" string="Orders"/>
                </button>
            </xpath>
        </field>
    </record>
  </data>
</odoo>