To do this:
1. Select Playing Now in the Tree (it doesn't matter which one, you just want to select something OTHER THAN Audio, Images, or Video).
2. Go to View > Add View > Add Library View.
3. In the dialog that appears, choose Empty View, and name your view "Advanced" (or something that makes sense to you). Make sure the Location is listed as (root), and click OK.
4. In the Customize View dialog that appears, add appropriate Categories. I'd suggest that you use these three as the first three, at least:
Location
Media Type
Media Sub Type
For Location, you pick the File Path option under Type when adding a new category, and then just leave the Select Path box blank.
5. When you've added appropriate Panes, click the Set Rules for File Display button under Settings.
6. Add a Sort By rule to the Modify Results section, and have it sort by: Filename (a-z)
7. Ensure there are no other filters added to the search rules.
8. Set Position to Bottom (so it sorts under Audio, Images, and Video in the tree). You may also want to uncheck the Support Tree Browsing box.
9. Done.
Now, you'll have a view that shows EVERYTHING in the normal MC Library, and allows you to filter it by Media Type, Sub Type, and File Location. If you can't find the files in there, then they aren't imported, but if you can, then they're tagged wrong.
I had you add the panes and whatnot directly to the Advanced view in the tree. In practice, you may find it nicer to make a set of sub-views under the Advanced top-level views, with a variety of different filters and sets of panes. For example, you could follow steps 1-3 above, and then uncheck the Allow tree selection item in the Customize View dialog. This makes the view into a sort-of "folder". Then, you can add a separate sub-view (maybe called "Disk Location" or something) that has the actual Panes you want to use.
