Hello!
I have been trying to get it to work and adapt it for quite some time, but given that the plugin depends on many functions from Scene_Items, its functionalities are not available during battles. (In fact, personally, that's why I usually don't make plugins related to battles because they are a headache.)
I even tried to create another dedicated plugin in an attempt to simulate its operation, but I cannot get it to work properly. Here's a proof of what I have attempted at least xD
But as you can see, the filters are not resetting correctly, and I don't understand why. It's as though the Window Items in battle are not refreshing things once the filter is applied... I'm sorry, but I think I won't be able to fulfill this request. :(