pos/pos_customer_display_currency/views/pos_config_view.xml

<?xml version="1.0"?>
<odoo>
    <record id="view_pos_config_form" model="ir.ui.view">
        <field name="name">pos_customer_display_currency.pos.config.form</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='customer_display_line_length']/.." position="before">
                <div class="row">
                    <label for="customer_display_currency_char" class="col-lg-3 o_light_label"/>
                    <field name="customer_display_currency_char"/>
                </div>
            </xpath>
        </field>
    </record>

</odoo>