partner-contact/partner_employee_quantity/views/res_partner_view.xml

<?xml version="1.0" encoding="utf-8" ?>
<odoo>
    <record id="view_partner_form" model="ir.ui.view">
        <field name="name">Partner form with employees</field>
        <field name="model">res.partner</field>
        <field name="inherit_id" ref="base.view_partner_form" />
        <field name="arch" type="xml">
            <page name="internal_notes" position="inside">
                <group>
                    <group
                        name="employee_quantity"
                        string="Employee quantity"
                        attrs="{'invisible': [('is_company', '=', False)]}"
                    >
                        <field name="employee_quantity" />
                        <field name="employee_quantity_range_id" />
                    </group>
                </group>
            </page>
        </field>
    </record>
    <record id="view_res_partner_filter" model="ir.ui.view">
        <field name="name">Partner search with employees</field>
        <field name="model">res.partner</field>
        <field name="inherit_id" ref="base.view_res_partner_filter" />
        <field name="arch" type="xml">
            <filter name="salesperson" position="after">
                <filter
                    name="employee_quantity"
                    string="Employee Quantity"
                    domain="[('is_company','=', True)]"
                    context="{'group_by': 'employee_quantity_range_id'}"
                />
            </filter>
        </field>
    </record>
</odoo>