For most of the nodes displayed in the tree you can obtain a popup "alter-ego" menu. How you do this is platform-dependent, but you will typically click with the right mouse button on the name of the node.
Here is an example of the menu you might get from a Starlink NDF file:
The other lines give different icons and different kinds of nodes which it can be viewed as. An NDF can be seen as an HDS structure, or as a Starlink NDX structure, or simply as a normal plain file in the directory structure. So if you pick the bottom line on the menu, the NDF icon will disappear from the tree to be replaced by a plain icon representing a file, and you will only be able to see its size and last modified date. You can popup a menu on this node in turn and change it back into an NDF or into one of the other selections you are given.