Here I will talk about left frame of administrative console, where main navigation menu is located. We usually call it "tree", since it looks like one.
There 2 tree node types in tree:
Folder can have items inside them, items can't have anything inside them.
Folders can be containers (folder click actually click on folder's first item) or not (folder click performs click on that folder).
Items of the folder could be defined from the start and could be loaded dynamically via ajax.
When folder contents is static and it is container, then all works.
When folder contents is dynamic and it is container, then folder click happens instead of click on it's first item.
To test need to set 'container' => true
and remove 'onclick' ...
from main catalog tree folder (defined in "sections_config.php").