If you mean the list A-B, C-D, E-F etc with the folders that are under the main block on the IDwiki page (the wiki index), you would be able to hide those by setting all areas' Display Order to 0. I'm not sure, but it might mess up the order of the areas when you are using the search or creating a new page. There's still a lot we can do to improve the wiki index (and other pages), like giving per-page settings about what blocks are supposed to show there (e.g. the "Wiki Areas" block you don't like), but for now this is what we have.