Hi Clive
That feature would be great as I also use the date added to sort music, to a certain degree. I have defined a workaround for this where I use a field in the MP3 tags that is not used at all, or generally not used. I use Original Composer, for example.
When I add new tracks to the collection I immediately add the date to that field. I can then use the Intelligent Playlist feature and filter by that. Just check what fields are visible in the Intelligent filter options and then see if one of those fields would work best for you.
Also, by recording the date added in that field it is never lost, even if you move or recreate your collections.
Hope this helps.
Damian