We should as well store permalink to collection. If link is already in Database then we only updating it and not writing new Collection.
I managed to "hook" into the mechanism you use to add new items to a collection. It does not work on all subpages, but a new button appears when you add an item to a collection. It is a checked checkbox that says it will add the item to the extension's list. So if you should not want to add it, just uncheck the checkbox.
So in theory you should only populate your collection list once and then just browse and use itch regularly.
I am currently concerned about game ids. I saw some that seemed to be recycled. If that is possible, I might have to switch to gamelinks, instead of ids. The ids at least seemed to have been recycled by the developer. But maybe I am mistaken. It was "old" ids that have recently been published. The problem with game links, developers sometimes change their name or the link of the game. It is a problem for the regular collections too, but I think this is because they create a new project with the old name.