I have been recently editing artist metadata to update many of the photos. Drag and Drop has never worked for me (OSX 10.11.6), which should probably be filed as a separate support request.
The photos I wish to attach are most often in my “Downloads” folder, which has a very large number of total items. It would be very useful to be able to display the contents of this folder by date using the Roon file browser. Without this feature, the folder contents are listed only alphabetically (and not searchable); it is almost impossible to find the correct image.