I use Transmission on Mac for handling my torrents. I just reformatted and reinstalled Transmission. How do I go about letting Transmission know that the .torrent files I have, are already downloaded and to start seeding without starting downloading again?
If the torrents live in the torrents destination folder (look in Edit -> Preferences, then the Torrents tab), then Transmission will just figure it out & you don't have to do anything.
If the torrent files live somewhere else, just make a symbolic link from the torrents download directory to their current location.