When you have a large document, the Page Thumbs are not very helpfull, so I love to have a vertical-scroll option where you can see all the pages at once. Is that possible? Something like this
Interesting idea. I'll pass your feature request along.
In the meantime, you can try modifying the CSS in the exported pages.css file using the Resources section in the Export HTML5 with in5 dialog (in5 > Export HTML5 with in5...).
Or you could manually make a pop-up with thumbnails by doing the following: