oca-technical/odoo-bringout-oca-pos-pos_payment_restriction/pos_payment_restriction/views/pos_config.xml

<?xml version="1.0" encoding="utf-8" ?>
<odoo>
    <record id="view_pos_config_form" model="ir.ui.view">
        <field
            name="name"
        >pos.payment.terminal.config.form (in pos_payment_restriction)</field>
        <field name="model">pos.config</field>
        <field name="inherit_id" ref="point_of_sale.pos_config_view_form" />
        <field name="arch" type="xml">
            <xpath expr="//field[@name='iface_precompute_cash']/../.." position="after">
                <div class="col-12 col-lg-6 o_setting_box">
                    <div class="o_setting_left_pane">
                        <field name="payment_amount_readonly" />
                    </div>
                    <div class="o_setting_right_pane">
                        <label for="payment_amount_readonly" />
                        <div class="text-muted">
                            Payment lines amount would be readonly
                        </div>
                    </div>
                </div>
            </xpath>
        </field>
    </record>
</odoo>