Thanks for your support.
I only want to use manual relationships.
The only goal is to show 4 portfolio items in each product item and set this portfolio items in the product edit page.
I set “Enable Similarity Marker Categories (pro)” and now all portfolio and product items have a common category, but I don’t know if this is what i have to do if I wont to use manual relationships.
I think this plugin has so many options that it is a bit complex and confusing to set up.