[NavigationView] Tooltips are difficult to be changed

The text prompt in the navigation bar is hoped to be configurable, allowing control over whether it is displayed and the ability to customize the displayed text content.

Start by locating the Flutter NavigationView implementation and the code that creates its navigation-bar tooltips. Confirm how the current prompt is displayed, then make its visibility and text configurable; done means both controls work as requested and existing behavior remains intact when unchanged.

Written by the indexing model from the issue text.