You write a subtitle, then you're able to mark it as that and it will appear at the beginning of your book in a normal written (not hand-written) style.
Also i would love if the few last and the few next subtitles would appear next to the site you're currently using. While you can swipe horizontal to change the site you can scroll vertically to go through your titles and tap at it.
in the vertical (tablet) mode is a lot of blank space. would be great if it could be used.