I have a game on Steam currently with 4 dlcs and another dlc upcoming. It's a fairly large game that took 4+ years to create. It's been a Steam exclusive title since its early access launch and also it's full launch. I really would like to post this game here on itch.io as well. I am wondering is there a way to post the game with its dlcs here? For example, is there a way I can sell the Steam keys as on bundle sites? I could setup a full package edition but I will have to go through it all and dig out the dlc restrictions.

You can have multiple versions of a game at different price points, so you could have base game with all DLC disabled + base game with all DLC installed available as different options. (For instance either including the expansion files in the full-package version, or compiling two different versions of the executable with DLC checks hardcoded to either "no" or "yes") There's no itchio-intrinsic way to make it more granular than that at the moment, though. (You can have any number of tiers but it doesn't really make sense for DLC that don't have ordering dependencies, like character packs)