Sure, I could do that, and I don't mind driving command-line tools to do the tag modification so that's no real problem, but even with a 99.9% success rate, the

Sure, I could do that, and I don't mind driving command-line tools to do the tag modification so that's no real problem, but even with a 99.9% success rate, the size of my music library makes manually fixing up the ones that don't come out right a considerable task -- to say nothing of identifying them in the first place, another problem which doesn't really admit of easy programmatic solution. In theory, I suppose I should just block out a weekend day or so, put on my headphones, and bite the bullet. But being able to add playlists, as playlists, to playlists, would neatly solve the problem without requiring me to spend a day engaged in such drudgery, and would offer other UI benefits besides. What I've got right now works well enough to be going on with for most of my purposes, and I suppose I just keep hoping someone will come along and satisfy my now rather forlorn hopes as to the rest.