Hide Tracks/Albums

As I use MP3TAG to clean up the tagging structure of albums, a useful feature would be the ability to hide (temporarily or as a persistent attribute) tracks/albums/folders. I would use such a feature to remove from the list view those items that are satisfactorily tagged. Optimally this would be a persistent (but reversible; e.g. "unhide all") state so that the process of correcting tags can span multiple sessions and newly added items would be unhidden until satisfactorily enriched with metadata.

If this feature already exists and I have failed to discover it, I apologize.

Not exactly - but you can use a filter to show only tracks that match certain criteria.
See the help for filter expressions.
You refresh the filtered list by presssing F3 twice (which deactivates and then activates the last filter).