You cannot, AFAIK.



Have you tried using, instead, the Navigation Pane together with Outline view?

The Navigation Pane will only show items which have outline levels and you can decide how many levels to show.

Thank you. I never used the Navigation Pane so I experimented a few minutes.
Yes, I think it can help, but I will have to adjust my working habits.

Also, the Navigation Pane uses valuable space at the left side of my monitors, especially when I use long headers.

Nevertheless, it is a step forward.
Again: thanks.