I would like to suggest a configurable popup/seperate/dockable panel that shows the current keys as clickable buttons on a "Navigation Panel", based on the current navigation type.
Available mouse actions could also be shown.
Viewpoint cycling and info as well as current position and orientation could be shown.
WorldInfo could be available on an About button.
NavigationInfo info and controls for avatarSize, headlight, speed, visibilityLinit, and navigation type could also be controllable from the NavigationPanel.