I created an action button on the form view stock.view_picking_form. The button should open the same tree / form view with the return operations of the active partner on the form view from which I am starting (I know that they are return operations through a custom field populated at the time of the creation of the return record on stock. picking). I would like to know if the value of partner_id is available in that time and how it can be referenced in domain or in search_default context. My code is:

    <record id="act_return_carico_fiduciario" model="ir.actions.act_window">

            <field name="name">Restituzione carico fiduciario</field>

            <field name="res_model">stock.picking</field>

            <field name="view_mode">tree,form</field>

            <field name="domain">[('cf_end_date','!=', False), ('partner_id'), '=', ????????]</field>

           <field name="context">{'search_default_partner_id': ????????}</field>

            <field name="groups_id" eval="[(4, ref('sales_team.group_sale_salesman'))]"/>

    </record>

    <record id="view_picking_form_inherit_carico_fiduciario" model="ir.ui.view">

        <field name="name">stock.picking.view.carico.fiduciario</field>

        <field name="inherit_id" ref="stock.view_picking_form"/>

        <field name="model">stock.picking</field>

        <field name="arch" type="xml">

            <div name="button_box" position="inside">

                <button class="oe_stat_button" name="%(carico_fiduciario.act_return_carico_fiduciario)d" string="Restituzioni" type="action"

                    icon="fa-ticket" help="Restituzioni TdV" attrs="{'invisible': [('enable_car_fid', '!=', True)]}">

                </button>

            </div>
............

Can someone help me? thank you