They were planned to alter stat variables, which became too time consuming to figure out with RenPy. Anyone is more than welcome to alter and finish it :) RenPy is open source
I'll add this to the devlog, but really the only inventory items you need are the keys to get to other rooms. A few others will prompt other story options, such as getting the script for the librarians. There isnt anyway to "craft" or "use" the items
