The icon for Flow mode shows a viewport with the bottom half of one page on the top followed by the top half of the next page underneath it.
But I've found that when I activate Flow mode this only happens for regular pages. Certain boundaries such as ends of chapters do not scroll, even with Flow mode on, they jump.
You scroll to the bottom of the chapter, and then instead of having those lines go up the viewport, and seeing the lines of the next chapter appear on the bottom, it skips the whole page.
Is there a way to get Calibre to do this?