I received the following coimment on Issue 425.
In text view, Shift+PgUP/PgDn does nothing. The key combination works properly in code view. It should highlight approximately 10 or so lines above or below the caret. You can accomplish the same thing with multiple applications of Shift+UpArrow/DnArrow.
Shift+PgUp/PgDn is standard in all editors I have used.