I saw some years ago there was going to be something similar in the form of sub products, but I don't see the option when adding a new project?
Any help appreciated!
From what I remember, sub products have been put on the side for now.
I think the best way to make DLCs is to make a new page for each DLC, and mention details of how to use it, and that it’s part of another project.
How would that require the user to own the original game?
It wouldn’t. Using that method means it would be up to you to explain that in the game’s page.