A stock column called Contents [S] normally shows the number of files inside a folder. But I bet few of you know that this column is adjustable through the szFileCountRule registry tweak:
So if we set szFileCountRule = *.JPG,*.PNG (using Tools > Advanced options menu command) the Contents detail will return the number of JPG/PNG files in a folder instead of the total file count. We can then use this column to find folders that have no album art in them, i.e. folders where this count is 0.
If we don't want to tweak the registry each time we need a different wildcard for szFileCountRule, we set it once and for all to a saved filter name, then we alter the definition of the named filter, which is possible while xplorer² is running. This way we can use more complex criteria for the Content [S] column, not just filenames. Here's a demo video explaining the steps:
To recap, the steps for searching for missing files are:
you only have to do this step once
Whenever you need to search for different missing files, just repeat the steps 1-2 defining a new search pattern for cntRule. Or if you want to restore the contents column to count all files, save cntTool to an all-inclusive wildcard like *.*
This solution isn't as thorough as the aforementioned WSH script as it won't check if the examined folder contains music file types, it just reports folders without pictures in them. But if you search within My Music folder, all subfolders will have MP3 files in them implicitly. It all depends on how your folders are organized and how do you define what's "missing". Just extrapolate for your needs!