Thanks for the responses everyone, I'll try and reply to them all.
Pingaware: I have a static playlist - I want to set a specific sort order for it, e.g. using 'sort title'. I then want it to just stay with that sorting, regardless of what I do to other playlists, whether I close & reopen MB, whether I add or remove songs to/from the playlist, etc. I might change this sort order to something else, either temporarily or permanently, but whatever sort order I choose I want it to stick.
I've tried right-clicking on the playlist node, as suggested elsewhere by Steven, and selecting 'custom fields...' in the playlist settings. This is supposed to make the sort settings stick, but it doesn't work for me.
Freddy Barker: I don't want to make the playlist read-only, because I want to be able to add or remove items from it or otherwise change it, and presumably this wouldn't be possible. I just want the sorting option I choose for a playlist to stick.
Frankz: Updating the play order does exactly that - it updates the play order. It doesn't make whatever sorting option you've chosen stick (at least not for me) - although it does provide a sort of snapshot of the current sort. But if you add or remove a track, or change sorting on another playlist, the sorting sometimes changes. What I want is to sort a playlist a certain way and for it to stay sorted that way regardless of what else happens - until I change it to something else. Updating the play order, and then using 'manual order' to re-sort with seems even less efficient than having to check the sorting order every time you look at the playlist...
So my question is still the same, and it seems incredible to me that this is such a thing. Why can't I sort each playlist the way I want, and then forget about it? As I mentioned in my original post, Steven seems to be against this idea, but surely someone out there must have worked out a way around it. Or has anybody else found that the 'custom fields' option fixes the sort order permanently as Steven suggests? It certainly doesn't for me.
Thanks, Simon