In the F5 Navigator Dialog there are “next page” and “previous page” buttons that put the top of the target page at the top of the viewport (i.e. they do what the reader of a real book does by “turning” a physical page.)
Some years ago (2016) a query about this sort of thing was marked as “solved” but, in fact, the ToBeginninOf[Next/Previous]Page function cited in that “solution” only moves the cursor to the first line of the target page without putting that line at the top of the view port. So far as I can see, there is no item listed in Tools>Customize>Navigate>Functions that accomplishes what I call a BookPage change, and therefore I cannot reassign the PageUp and PageDown keys to do what I want them to do.
Obviously the code for BookPage changes already exists (otherwise the buttons in the Navigator dialog would not work as they do) so, it should not be much trouble to give that function a name and include it in the Tools>Customize>Navigate>Functions list.
I hope someone can make that happen.
Thanks.