odoo-product-addons/product_variant_description_sale/views/product_product.xml

<?xml version="1.0" encoding="utf-8"?>
<odoo>

  <record id="product_variant_easy_edit_view_inherit" model="ir.ui.view">
    <field name="name">product.product.view.form.inherit</field>
    <field name="model">product.product</field>
    <field name="inherit_id" ref="product.product_variant_easy_edit_view" />
    <field name="arch" type="xml">
      <group name="tags" position="after">
        <group name="description" string="Sale descriptions">
          <field name="description_sale" readonly="1" string="Product" />
          <field name="variant_description_sale" string="Variant"
            placeholder="This note is added to sales orders and invoices for this particular variant." />
        </group>
      </group>
    </field>
  </record>

  <record id="product_normal_form_view_inherit" model="ir.ui.view">
    <field name="name">product.product.view.form.inherit</field>
    <field name="model">product.product</field>
    <field name="inherit_id" ref="product.product_normal_form_view" />
    <field name="arch" type="xml">
      <group name="description" position="attributes">
        <attribute name="string">Sale descriptions</attribute>
      </group>
      <field name="description_sale" position="attributes">
        <attribute name="nolabel">0</attribute>
        <attribute name="string">Product</attribute>
      </field>
      <field name="description_sale" position="after">
        <field name="variant_description_sale" string="Variant" attrs="{'invisible': [('product_variant_count','=',1)]}"
          placeholder="This note is added to sales orders and invoices for this particular variant." />
      </field>
    </field>
  </record>

</odoo>