I think "Save as HTML" is what you need - you will have your map in a form of listed nodes.
(to save your map as an HTML file click on "Save as" button and choose ".html" in Save as type drop menu)

If you need pure text without icons or images, you can copy everything from HTML file (Ctrl+A, Ctrl+C) and paste into text editor (that doesn't support images - e.g. Notepad) and save it as a .txt file.