I hope that I don't need to revert back from this one.
So, now you should be able to toggle the prepared-status without a page reload. Use the stars. I noticed that you sometimes need to hit the stare twice so be patience. After the toggle you do need to change the filter or sort once. So if you only filter on "Prepared" and hit the filled stare to turn it off, you still need to change the filter or sort the spells in another order. Im gonna tweak this a bit.
Please let me know if you find strange behaviour with this (more than just the double-click and need-to-sort), It's something that need to be tested over more time.