איפה הקוד שמכניס את תיאור הקובץ שהועלה לעורך?

The goal is just to understand where in the discourse code the code is that puts that text into the text area.

If it’s helpful to have a specific use case, how about: how would you change that text to something else?

If it makes a difference whether I’m doing a plug-in or theme component, I’m fine doing either.