You may want to collapse the navigator automatically as soon as you open a page. This gives you more space to work with page. The navigator will automatically reappear as soon as you close the last page/multi-page view.
On the Opening subtab of the Extra tab on the Preferences dialog box, tick the Auto-close navigator on page opening setting. By default it is not ticked.
Note
It uses the variable F_HideNavOnOpening.