I found two archived posts about this from 5 years ago that never went anywhere:
https://itch.io/t/261383/more-advanced-permissions
https://itch.io/t/270049/individual-permissions
as well as this github issue
https://github.com/itchio/itch.io/issues/1271
The official way seems to be to create a collection and display the collection on your page then according to the github issue, though i have not tried that yet.
Its dissapointing that this is not possible directly, i have a project that my team continued for another team, they of course want to display it on their page as well but i dont know them, and i would prefer if they dont have permissions to upload builds anymore and such as they are not part of the team anymore. This is not just about the possibility of them defacing the page, but also a feels like a security risk, if every collaborator who wants to display a game on their page can also upload new builds as an admin?
Is there really no a way to add someone as a contributor without giving them admin rights? Or giving someone only the priviledge of working on the page but not uploading new builds?