not sure if they will make it possible to do the install later but here a work around i have found
- install "ProjektPassion-0.4pc" using the app
- then go to manage and open folder there will be two folders one that say ".itch" and another "ProjektPassion-0.4.1-pc"
- delete the folder "ProjektPassion-0.4.1-pc"
- then you can download the new update "projekt-passion-win3" from the website
- after extract the file you download to get "ProjektPassion-0.16-pc"
- then just cut and past the "ProjektPassion-0.16-pc" in to the "ProjektPassion-0.4pc" folder
- after that you should be able launch the game from the app
hope this helps at all I'm not great at explaining