pos/pos_user_restriction/views/pos_config_views.xml

<?xml version="1.0" encoding="utf-8"?>
<odoo>
    <record id="pos_config_view_form_users" model="ir.ui.view">
        <field name="name">pos_config_view_form_users</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="//sheet/div[last()]" position="after">
                <h2 groups="point_of_sale.group_pos_manager">Users</h2>
                <div class="row mt16 o_settings_container" groups="point_of_sale.group_pos_manager">
                    <div class="col-12 col-lg-6 o_setting_box">
                        <div class="o_setting_right_pane">
                            <div class="text-muted">
                                Users assigned to this point of sale
                            </div>
                            <div class="content-group">
                                <div class="row mt16" title="Restrict some users to only access their assigned points of sale. In order to apply the restriction, the user needs the 'User: Assigned POS Only' group">
                                    <label for="assigned_user_ids" class="col-lg-3 o_light_label" />
                                    <field name="assigned_user_ids" widget="many2many_tags" options="{'no_create': True}"/>
                                </div>
                            </div>
                        </div>
                    </div>
                </div>
            </xpath>
        </field>
    </record>
</odoo>