Photoshop Elements :: Remove Multiple Folders From Organizer 12?

How do I remove multiple folders from Elements Organizer 12, without deleteing the folders?
 
I imported all my pictures into Organizer. As it turns out, that included dozens of subfolders containing near-duplicate images, which now all show up in Organizer. That is because I previously used Google Picasa, which backs up the unprocessed original images into a subfolder called .picasaoriginals. I want to remove all these .picasaoriginals folders, but the only wny I can find to do it is to right-click each one individually, click Delete Folder, then confirm in the dialog box. I can't find any way to multi-select the folders.
 
Also, I have two of these folders that appear shaded in the folder list, where the option to delete is greyed-out. The contents report as not found, and my guess is that the folders have been deleted from the disk. How do I get rid of these from the folder list in Organizer?