Add new feature;
at the bottom of a text be able to draw a non-printable horizontal line on screen
I've seen that many people get really confused when at the end of a document there are several blank lines and things like adding extra pages etc are influenced by that. The obvious solution is to paint a helper line to show where the text ends.

Additionally, when there is more text in the frameset then there is shown, paint a non-printable "plus" sign in the bottom-right of the last frame.

I've often seen professional editors forget to layout the last couple of paragraphs because they were not visible in the document anywhere. Which makes this indication a life-saver.