You can now prepare and un-prepare your spells in a spellbook, just toggle the stars. I'm sorry for the page-reload between every click but it seems like I dont have much free time on my hands. An update WILL come.
Ofcourse you are able to filter the spells by prepared under the /view spellbook-page.
Filter by Prepared and then choose how you would like to sort them. Level and Name is my favorite. How about you?