use a multifile text editor (I use textpad for example) to open all json files, then make a multifile search for the filenames. This will find all references, although it might take some careful checking to get back to the editor variants of the references (storage is by id number)
It's been a weird while. I've been so torn down that even playing video games has been something I avoided. But I shouldn't forget two things. One, I love RPG Maker for a reason. Two, only way to eat an elephant is a bite at a time.