Hello,

By odoo standard flow, all the product variant with respected attribute name will be shown in sale order lines.

And if you want to show the attribute value of product in order lines, then you need to take a new many2many field for product.attribute in order lines like

    product_template_attribute_value_ids = fields.Many2many('product.template.attribute.value', relation='product_variant_combination', string="Attribute Values", ondelete='restrict')

You need to set product.attribute value while onchange method of product in order lines model.

    @api.onchange('product_id')

    def product_id_change(self):

        super(class_name, self).product_id_change()

        if self.product_id.product_template_attribute_value_ids:

            self.product_template_attribute_value_ids = [(6, 0, self.product_id.product_template_attribute_value_ids.ids)]

Thanks.