I understand that I cannot change the three basic files --Draft, Research, and Trash. However, the Tutorial suggests that it is possible to add other headings. For instance, I would like to add a major file that contains character sketches and location descriptions. How do I do that?

That’s easy. Just create a new folder anywhere and drag it on the topmost level of the tree. (You’ll see a black line marking where it will end up once you let go. See that the black dot at the left end reaches the left side of the binder.)

I usually have several additional folders - “Org”, where I put everything concerning deadlines, important mails with the editor etc., “Crew”, where I develop my characters, each one in a different document (sometimes I make even subfolders for main characters, minor characters and the rest), “World”, where I note everything regarding the settings, and so on. I put them all before the “Draft” folder (which can be renamed; I name it with the working title of my novel).

You can as well drag documents on top level. I usually have one where I keep a writing diary.