@johnjohnston Looks like a handy tool! Another method for tagging in Finder is using the built-in keyboard shortcut (Control-5) to tag the selected files in blue.

Use keyboard shortcuts to tag files quickly—select a file, then use Control-1 through Control-7 to add (or remove) your favorite tags. Control-0 (zero) removes all tags from a file.

Use tags to organize files on Mac