How can I run a search to see what music files are still in the Library but in fact no longer exist, please.
The answer to this question is: Open a view that lists
all files in your library, then, paste the code below into the search bar in the top right.
Be warned though, this checks the existence of each file in your library, one after the other, and, depending on your library size, could take a while a to complete, so be patient. The resulting list will have have files that are in your library but cannot be found on disk.
Also note, I make use of MC's "Notes" feature, and also have HLS streams stored in my library... both of these types turn up in this resultant list and are safe to ignore.
[=ismissing([filename])]=1
Run auto-import is on
OK, but, under your "auto import settings", (
Tools > Options > Library & Folders > Configure Auto Import), how are you set for "Fix Broken Links"?
For what you seem to expect, it should be set to, at least, "Yes, Protect files on missing drives", unless, of course, your files are stored on removable drives, but then, you'd still want that set that way, and then, absolutely, follow Jim's advice and delete via MC only, then, it will keep up with you easily
-marko