Automatic Tag Folder Action

1. Already have an arbitrary named folder created on your Desktop (e.g. Tag_Items, etc.).
2. Dock : Launchpad : Other : Automator.
   1. New Document : Folder Action : Choose.
   2. Automator will open into two narrow, left columns (Libraries, Actions), and a central larger workflow window.
3. In the Automator library, drag and drop the Run AppleScript action into the larger workflow window. On earlier releases of OS X, this will be in the Utilities library.
   1. At the top of the workflow, use the selector to choose the folder that you wish to drop files.
   2. Replace the entire contents of the Run AppleScript boilerplate that you just dropped into the Workflow window with the scrollable AppleScript contents at this previous post location. The trick is to click in the very top left corner, and drag downward to select everything in that scrollable window, before copying and pasting into the now empty Run AppleScript action.
   3. Once the content has been pasted into the Run AppleScript action, verify that all was copied and pasted from the above scrollable window, and then click the hammer icon to compile the AppleScript.
4. Save the Automator Folder action by any name you choose (e.g. N-Tags to Folder, etc.).

   This will be written into ~/Library/Workflow/Applications/Folder Actions.

5. Right-click on the folder you chose as a drop folder, and select Services : Folder Actions Setup…, and Mojave will interject a dialog to confirm service. Click Run Service, and you should see checkmarks:
   
   and your selected folder is now ready to received dropped files, and run the AppleScript action.
   

The macOS Automation site can get you started with Automator.

The solution that I wrote in Summer 2017 that you linked to does not recursively assign selected Tag names to a hierarchy of folders or their files. As written, it was intended to add tag names to one or more individual files or folders dropped on the designated folder. To that end, it still works without change in Automator, using a single Run AppleScript action, on Mojave 10.14.1.

What you are asking for with that folder hierarchy request is additional, involved coding, and substantial time to test, and get working correctly. The code already gets all default, and custom tag names presently found in the Finder preferences.

Will you be assigning tags to only folders, and their folder children — or PDF files within these folders and sub-folders? Will you ever want to assign tags only to the parent folder, and not its contents, or sub-folder hierarchy? This can get pretty tricky depending on your goals.

Folder Actions only affect the item dropped on them, and then the action ends. A dropped folder will receive tags, but not its file and sub-folder children. This means that the economics folder will receive tags, but none of its contents, including micro/macroecomics folders will be affected. This is a limitation of drop folders not walking the folder hierarchy.

Another Automator solution would not use a drop folder, but could still be a drag/drop application that would optionally allow you to create a new folder, and then copy the selected folder hierarchy into it, applying the selected tags to all content, just folders, or just files. Now, programmatically you have more control over the chosen folder hierarchy tag solution without drop folder depth limitations.

You are welcome.