[A-l-l-a-n-o-n]

For me it works with U-Torrent (u torrent, version 2.2.1)
When I have a torrent, already seeded on one tracker and I want to seed it on another tracker, there opens a little Window with a warning sign from u-torrent, that this torrent is already on the torrent - list for seeded torrents and if I am sure that I want to seed it on another tracker as well. I simply click on YES and the torrent will be seeded on the other trtacker simultaneously
Hope that helps as an answer.