unless I missed something, a proper DLC support is missing. What I mean? Simply, on Steam I can create a DLC for the base game very quickly. Here I can do an extra version with game+DLC, but it's not very practical if for example there are 3-4 DLCs.
base game + DLC 1 + DLC 2 + DLC 3
would be much more convenient if was possible to upload the base game, and then the DLC as separate upload/downloads, so players could buy them individually (maybe some players like DLC1 but not DLC2, etc).
Instead right now the only solution is to make each combination of base game + the various DLC and honestly it's not practical.
In summary having the possibility to upload a subfolder/files of the main project as DLC, like:
gamedirectory/ => upload it as base game
gamedirectory/DLC1/ => upload it as DLC 1, in the itchio app should be possible to download and MERGE the content, not REPLACE the base game
and so on for all the various DLCs. Of course with the download system wouldn't be much practical but that's fine (if people want to download DLC1.zip and then manually unzip it in the game installation folder, well they can always do it).