Best way to organize groups of books

[mb2u]

I use a Kobo Touch with firmware 2.5.2. I'd love to fill it with tons of reference material but 2 things get in the way.
1: They double space lists of titles wasting vertical space. Is it possible to correct this? Its crucial to scan as many titles as possible per page.

2: They use large fonts. Is it possible to control the font size used in these directories?

"Shelves" seems to be a good idea of organizing stuff but is it possible to have more than 1 sub-folder? Most of us several sub-folders when organizing material. I can't understand why ebook manufacturers don't realize these devices are great for reference material but that only works if you can find something easily.