So I have this tweak in my mind and I would like to know whether you guys approve it or not.
I suggest that CK recipes will now be tome-based i.e your hero will consume it right on the spot to level up the respected CK. If you would like to hold your CK recipes you can use your boxes to contain them. This will effectively remove the annoyance of having to free up inventory slots to get a CK if your characters' inventories are full.
This won't cause bugs because I know what I am suggesting.