Hi,

In your module, create a Python file (e.g., models/models.py) and define a new model to store the custom field.

from odoo import models, fields

class ProductTemplate(models.Model):

    _inherit = 'product.template'

    engraved_number = fields.Char(string='Engraved Number')

In the same Python file, extend the product variant form view to include the custom field.

from odoo import api, fields, models

class ProductTemplate(models.Model):
    _inherit = 'product.template'

    engraved_number = fields.Char(string='Engraved Number')

class ProductProduct(models.Model):
    _inherit = 'product.product'

engraved_number = fields.Char(string='Engraved Number', related='product_tmpl_id.engraved_number')


Create an XML file (e.g., views/product_variant_view.xml) to modify the product variant form view.

<odoo>
<record id="product_variant_form_inherit" model="ir.ui.view">
<field name="name">product.product_template_only_form_view</field>
<field name="model">product.template</field>
<field name="inherit_id" ref="product.product_template_only_form_view"/>
        <field name="arch" type="xml">
            <group>
                <field name="engraved_number"/>
            </group>
        </field>
    </record>
</odoo>

Hope it helps