If you want to add/delete tag to file, we can use SetAttr META with keyword (e.g. SetAttr META encoder:Me to add or SetAttr META encoder:* to delete).
In July 2016, new tag 'Encoding Software' tag was created.
Problem, we can add tag with meta pane, display column with {mp3encodingsoftware}, but I need to know keyword to add/delete tag with SetAttr command.