Hello Rickard Wallster,

On Purchase Order Line, Product search window If you want to display "[Internal Reference] Product Name" instead of the "[Supplier Product code] Supplier Product name". Then you need to overwrite the base product.product 'name_get' method and you need to remove If/else condition for the seller. I have modified the below method as per your requirement you can use this method.

Please inherit product.product object in any custom module and you can add the below method.
Note: Below method was copy from odoo v12.

@api.multi
def name_get(self):
# TDE: this could be cleaned a bit I think

def _name_get(d):
name = d.get('name', '')
code = self._context.get('display_default_code', True) and d.get('default_code', False) or False
if code:
name = '[%s] %s' % (code,name)
return (d['id'], name)

partner_id = self._context.get('partner_id')
if partner_id:
partner_ids = [partner_id, self.env['res.partner'].browse(partner_id).commercial_partner_id.id]
else:
partner_ids = []

# all user don't have access to seller and partner
# check access and use superuser
self.check_access_rights("read")
self.check_access_rule("read")

result = []

# Prefetch the fields used by the `name_get`, so `browse` doesn't fetch other fields
# Use `load=False` to not call `name_get` for the `product_tmpl_id`
self.sudo().read(['name', 'default_code', 'product_tmpl_id', 'attribute_value_ids', 'attribute_line_ids'], load=False)

product_template_ids = self.sudo().mapped('product_tmpl_id').ids

if partner_ids:
supplier_info = self.env['product.supplierinfo'].sudo().search([
('product_tmpl_id', 'in', product_template_ids),
('name', 'in', partner_ids),
])
# Prefetch the fields used by the `name_get`, so `browse` doesn't fetch other fields
# Use `load=False` to not call `name_get` for the `product_tmpl_id` and `product_id`
supplier_info.sudo().read(['product_tmpl_id', 'product_id', 'product_name', 'product_code'], load=False)
supplier_info_by_template = {}
for r in supplier_info:
supplier_info_by_template.setdefault(r.product_tmpl_id, []).append(r)
for product in self.sudo():
# display only the attributes with multiple possible values on the template
variable_attributes = product.attribute_line_ids.filtered(lambda l: len(l.value_ids) > 1).mapped('attribute_id')
variant = product.attribute_value_ids._variant_name(variable_attributes)

name = variant and "%s (%s)" % (product.name, variant) or product.name
sellers = []
if partner_ids:
product_supplier_info = supplier_info_by_template.get(product.product_tmpl_id, [])
sellers = [x for x in product_supplier_info if x.product_id and x.product_id == product]
if not sellers:
sellers = [x for x in product_supplier_info if not x.product_id]

mydict = {
'id': product.id,
'name': name,
'default_code': product.default_code,
}
result.append(_name_get(mydict))
return result

Hope this may help you!

Thanks & Regards,

Email: odoo@aktivsoftware.com

Skype: kalpeshmaheshwari