I am using OS 10.9.5 with Lightroom 5. In the library module lightroom recognizes my image library on an external HD but will not recognize any other external drive in the library, but will recognize them when in file>import. Why will it not recognized the new HD in the catalog library folders list?
Lightroom lists only those hard drives in the folders panel from which you have imported images.
So, once you will import a few images from that particular hard drive, it will be listed in the folders panel.