[Azkahuna]

Wow, I am one happy camper. Thanks to the suggestions and ideas you guys have been so generous in sharing, I have come up with a solution that rocks! Perhaps it will help some of the rest of you.
I moved my entire Calibre Library to my external hd (1-TB), except for a library I labeled 'bookshelf'. I also put all my audio books, Video Tutorials and Opera MP4's on the ext hd as well, freeing up 250gb+ on my laptop.
On my ext. hd I created a 'Master Library' with a category for Genre, and a yes/no category for 'Bookshelf'
I created separate Libraries for Audio books, for video Tutorials and one for music, in addition to the ones I already had for Fiction, Magazines, Science Journals, etc.
Then I created an 'empty book' for each of my audio books, Opera recordings and video tutorials in the appropriate library, and using the 'Add files to selected book record' I added the appropriate file by first indicating 'all' in the file type drop down list. In cases where the audio book or recording, spans more than one file, I first created a playlist in Windows media player or BS Player pro, to include all the files in the particular audio book or tutorial series, saved the playlist, and referenced that.
After bulk identifying the metadata in each separate library to reflect the Genre of the library, (Audio book, Science Journal, etc.), and adding whatever info I felt was relevant, I transferred the books to the Master library. Now my library includes all my books, audio books and video tutorials which I can access directly from Calibre and includes whatever tags and information I want.
The reference books I access the most, and books, tutorials and videos I want to keep handy, I simply copied to my 'Bookshelf' library on my laptop. (Note: multiple file playlists will not play if the original files on the list have been moved or are not available, because only the list is moved, not the files the list refers to, but single audio/video files are transferred the same way as any single book, and as long as a playlist can access the location of the individual files, it will work as well. In cases where everything is stored on a single hard drive that is usually not an issue, but in cases like mine where the files in my master library are stored on my ext hd, and the playlist might be in my 'Bookshelf' on my laptop, it won't work if I unplug my ext hd. (Playlists reference files by relative accessible location).
Now I have nearly all my books, audio books, tutorials and Opera recordings accessible through one Master Library. I'm already starting to add my commercial videos as well. I keep a copy of my top reference books, books I want to read or reread, magazine and journal articles I haven't read yet, my most frequently listened to recordings, and most frequently used video tutorials (Maybe 300-400 entries total) in my 'Bookshelf' and simply remove them when I'm done, while the master copy stays on my ext. hd. In the case of tutorials and recordings I use frequently that span multiple files, I simply store all the associated files on my laptop, and create my playlist from them, then reference that playlist in my Master and/or Bookshelf Library.
I still keep multiple genre libraries on my ext hd, but that's just because it is easier to dump multiple publications into a genre library as a 'presort', instead of an 'unsorted' library, before I transfer them to my Master library. The majority of the time my 'genre' libraries are now empty or close to it.
I don't know if anyone else will find this feature useful, but I am thrilled. I am so grateful for the brainstorming you guys helped me with. MAHALO & ALOHA
P.S. While I understood what theducks said about metadata, I'm not sure what the point was since my concern had to do with the size of the entire library and the fact that you could only access a particular book from one library without doubling the total file size, if you wanted to access it from two separate libraries, rather than having the same file accessed from two different metadata files. But I thank you for your imput. For me the question is now moot. Aloha