Hi, With my factories, I am making products right, if I need say glass, plastic etc to do so, Do I have to add the to the products list if I purchase them from an external provider or just have them as a supplier? I currently have them as both.

Hope that makes sense. - Maybe you can even use my factory as an example.

Not sure I’ve understood your question…
You must add product X in the products list if you want to manufacture or sell it.