Namespaces are defined by β€˜.’ delimeters in filenames, especially for entries. The breadcrumb entry head above the given content is formed by the current entry’s filename, which is

Namespaces are built with the jekyll-namespaces plugin (see docs for details) and are the building blocks for the tree graph.

If there are missing levels in the namespace, they will still be processed by the template. They will simply be marked as a missing in the graph and the entry head + entry links.