Option to show only directories with scanned thumbnails.

[coolhandluke]

Since this program catalogs the location that all thumbnails refer to, it shouldn't be too difficult to have a switch where the directory tree shows either the full tree or only those branches with thumbnails.
While it would be more work, I would also suggest that this function be tied in to the filter so the tree would change based on what type of file you were looking for.

[xnview]

Perhaps it will be better to have a special items in categories filter pane instead of folder pane