Advanced NBT Tooltips would seem like a suitable place for a couple of features from a mod called Better Enchanted Books that is no longer maintained.

First, instead of saying something like Protection III, it would be nice to have an option to instead print Protection III/IV so people have a quick reference for the max level. This makes sense for both enchanted books as well as enchanted gear.

The other nice feature would be to have an indication as to which types of gear an enchantment applies, in the case of books. The attached image shows how this was implemented in the other mod. (The first suggestion is not enabled in the image but that was probably self-explaining.)