two more or less complex feature suggestions:
1. include/exclude filters based on file name patterns (glob|regexp) or physical attributes (size, length, bitrate, etc.), so that any "view" on the right shows only files matching this filters

2. the "non-directories" view means to show all files in the current and all recursively addressable sub directories in the right list view, after selecting a directory - yes it may be very slow, but if easy to turn on/off, easy to use.
In combination with the include/exclude filters above a good helper to work on a bigger count of stored files.

Best regards,