Append Newly Created Folder Name to Text File

Wondering if someone has advice for appending to a text file. I've created a rule that takes a portion of a file name, creates a folder and then encloses the relevant file inside the new folder.

The file names are usually in this format: item_cruft-123.3dm
The current rule uses matching to create a folder that just uses the "item" portion of the name ahead of the underscore.
Eventually each file gets nested inside the correctly named folder (the file itself maintains the original name with the cruft).

Now I am trying to figure out how to take the folder name (just the item section) and append that name to a running text file. Wouldn't require any additional structure, just want to append the file name as a new line to a single text file. Any advice?

You would need to write a script for this. Try searching the forum or even the internet at large as I'm sure such scripts are floating around.