Moving to a bonus item may work... though i'd think demos shouldn't be considered an extra.

Which game(s)? To my understanding you can only get DLC as a gift unless you own the game.

There may be an exception for CP2077 or The Witcher 3; But when you bought the physical copy it included a code. Plus since they are publishing the game they can ensure DLC between stores is compatible so if you bought a Steam copy, the GoG DLC would still be compatible.

Only for the sake of categorization would they be an "extra"; attached to the main game card.

I think Witcher 3 might be what I'm thinking of, but it still shows the potential: So just rephrase it a little, and presto: Or something more marketable, I don't know. I hate marketing teams.

Maybe. More than likely the best way to take advantage of that is if the DLC was a GoG exclusive, but you didn't want to prevent steam owners from being able to use it with their copy.

Regardless, i think it's agreed they handle demos here fairly badly.