I came across same problem. 

Personally i just installed the manufacturing module. that enables "Bill of materials" on your products, then created a second identical product that just use the main product as the only manufacturing part. Works great. 

Hello Kevin, 

In default Odoo behavior, You can select only one of your website and it will display product to that particular product only. 

But if you want to select multiple website for your single product then it is require some customization and need to do some R&D to break default Odoo workflow. 

Thanks & Regards,

​

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I got an error while pasting a code

I received an email requesting an Odoo mug. I clicked on the link, but I couldn't enter the address because the value in the country field doesn't include "ENG". I noticed that one of my previous posts suggested that I added it. However, when I click the link to go to the page and enter the address, I get a "403-Forbidden" error.

Hello.

I used this module to obtain this result. This is for version 13, but it also worked on version 14 :
https://github.com/ctmil/website_product_multiwebsite

Now I'm looking to create a similar module, but with ecommerce categories.