How can I select folders to add to my iTunes all at once?

I have all of my music based in a separate folder from my iTunes, and it is also backed up on an external hard drive in the iTunes library because I have my preferences set to "Copy Files to iTunes Media folder when adding to."

The problem is, when I click add folder to Library, I can only select one folder at a time. I want to add multiple folders, but not all of the sub-folders that are contained underneath the same folder. I used to be able to do this, with a window that allowed me to use the ctrl key to select multiple folders. I used to click the folder everything was in, and it would open that folder so I could select the certain folders I wanted. Now, I get a window only with a + next to folders that opens up the subfolders and I can only select one.

How do I get back to the other style of window? It is not my version of iTunes because I have updated it on all of my computers/laptops, and the one laptop I use iTunes with the most is the only one that gives me this problem. Moving my music folders (or even copying them) to a new folder to add them is not an option. I am dealing with too much music and I'm not willing to waste that much time, especially when I know there is an easier way that I used to be able to use.