Just for the heck of it I decided to try the other extension offered by cynwoody, the fr_tree_viewer and low and behold it also doesn't have that META-INF folder that I believe is only for Firefox, but it works!
So I'm going to compare the manifest.json files from both folders and see what I can from there.
By the way, the tree viewer is pretty cool too.
I used to use the tree viewer as well a few years. It is really interesting on some threads.Did you actually get both of cynwoody’s scripts to work?