Hi Paul:

You can customize the Invoice document and replace the field you don't want with the Sales Description field.

You can do that by develop a custom app and inherit account.move.line model and override method _get_computed_name as below:

If you want to get only sales description in Customer Invoice & purchase description in vendor bill:

class AccountMoveLine(models.Model):
    _inherit = "account.move.line"

    def _get_computed_name(self):
        self.ensure_one()

        if not self.product_id:
            return ''

        if self.partner_id.lang:
            product = self.product_id.with_context(lang=self.partner_id.lang)
        else:
            product = self.product_id

        values = []
        # if product.partner_ref:
            # values.append(product.partner_ref)
        if self.journal_id.type == 'sale':
            if product.description_sale:
                values.append(product.description_sale)
        elif self.journal_id.type == 'purchase':
            if product.description_purchase:
                values.append(product.description_purchase)
        return '\n'.join(values)

If you want to get only sales description in Customer Invoice and get product code and product name and purchase description in vendor bill, you will use the below:

def _get_computed_name(self):    
    self.ensure_one()
    if not self.product_id:
        return ''

    
    if self.partner_id.lang:
        product = self.product_id.with_context(lang=self.partner_id.lang)
    else:
        product = self.product_id
    values = []
    # if product.partner_ref:
        # values.append(product.partner_ref)
    
        # values.append(product.partner_ref)
    if self.journal_id.type == 'sale':
        if product.description_sale:
            values.append(product.description_sale)
    elif self.journal_id.type == 'purchase':
        if product.partner_ref:
            values.append(product.partner_ref)
        if product.description_purchase:
            values.append(product.description_purchase)
    return '\n'.join(values)