All my photos are in a mac photo library on the external hard drive. I just installed Adobe Photoshop Elements 15 and I'm trying to import my photos. I noticed there is no option to do that from the external hard drive (at least I don't see it). I can't copy the whole library back to my computer drive since I don't have enough space and coping single photos to a folder on a desktop would take forever. Anyone can help me here?
Although your original images may be on your external drive are you sure the Apple Photos app hasn't copied them into a Package folder that is hidden from the users view by default?
By default that Photos app is set to store all imported images in a hidden Pack folder located in your User Name folder someplace (the Home folder). That is unless you Manually changed where the Apple Photos app stores the imported images and or whether or not it just adds the images to the database file of Photos from where they are stored.
I would first start investigating where and what the Apple Photos app is doing with your images.