Given no navigation tree is defined in the configuration, the section titles for sub-directories should be determined by the following logic:

• if an index page is defined, use the title of the index page, hereby the title from the meta data of the index page should be prefered to the title from the markdown in order to allow using a different title than the actual page title for the navigation menu.
• If no index page is defined, keep the logic "as-is".

The user should be able to turn on/off this behaviour by a configuration option, e.g.

theme:
  features:
    - navigation.smart-section-titles