Add a category for items that have no gameplay value ("junk" category), so you know you can sell it or trow it away.
Store the books content in a journal somewhere, so you will have access to them anytime without carring them around. Or move it to "junk" once you opened them.
Keys should be automatically removed once you opened the door or a chest it was made for. Or again - move them to junk.
Subcategories in categories. In crafting i would love to have tools (like inkpot and quill) and ingridients separated.
