Can't you just remove all the tracks from the playlist and re-add them from the folder?
This would destroy my previous manual (!) sort order and probably the assigned Ratings
Fair enough.
Your end goal is to identify missing tracks.
So ignore the fact that a playlist contains tracks or file paths or whatever, and the problem becomes a simple task of comparing two text files.
1. Your playlist has a manual sort order, so first create a copy and display the
File Name column so you can sort them alphabetically.
2. Export the playlist in .M3U format.
3. The exported playlist will include the full file path, so open it in Notepad (or any text editor) and do a
Find and Replace to remove the folder path so you just have a list of file names.
4. Open a Windows Command Prompt.
5. Change to the directory containing your music files and generate a directory listing of the files in it.
If you're not familiar with DOS commands, enter the drive letter followed by a colon to change drives, then CD to change directories.
e.g.
M:
CD "Music\My Playlist Folder"
DIR *.mp3 /b > "Folder Tracks.txt"
This will create a plain text file in the same folder that contains all of the file names.
5. Now use a file comparison tool to compare the file names in the playlist with the file names in the folder.
I recommend WinMerge:
WinMerge
Bee excellent to each other...