Did you know you can do mass renaming of folders and files in MacOS without having to learn regex?
You can select all files in a folder, and then right-click “Rename” to do search/replaces.
But! You can also do this on nested folders. To do this the folders need to be visible, which mean you need to mass-expand them. Which you can do by selecting all, then pressing Command + Right Arrow (you’ll need to select all again to select all the new files).
You can also mass-collapse with Command + Left Arrow.