Add file reference to Note $Title or $Text?

Well, you can have references in a TB document by just using the $File attribute, making it a Key Attribute for this or that Note. It will load with the application associated with that file type, just as if it was loaded via Finder.

I think the beauty of TB is that each project is a single text file, making it very portable and transparent in terms of stored data. Making a TB project a bundle of files would change all that. However, you can approximate this if you want, by just creating a Curio project and drag a TB file into a Curio Idea Space (as either a file reference or a real file).