Thanks Juanka :) There is an option to *force* this page to become the new default new tab but that's unfortunately not something the use can choose and I don't like the idea to impose it to the user (same thing for the home page). If one day there's a way to do it through an option, I'll be happy to oblige. In the meantime, you can set the new tab page with "new tab override".
To arrange the folders and/or bookmarks order, you can simply do it with your bookmark manager, the extension uses that order.
As for the rest, I'll consider it when I have some time to work on these features.