Or any tool condition validity, for that matter. If I am switching out a counterweight on a wooden sword, it will tell me (in red) that I need a level 1 hammer in order to do so. Adding one to my inventory via JEI does not update the UI to show that it is now valid, even though I now have the materials necessary.

This seems a little bit inconsistent because the inventory does update when items are moved, highlighting valid materials for the given modification (e.g. cobblestone for the counterweight has an outline around it.)

Currently it only updates available capabilities when you open the UI, changing it to update when the player inventory changes should not be that difficult.

Fixed in 0.20.4!