qBittorrent official forums

Menu: Tools - On Downloads Done

I think there should be more alternatives. Why not an option that pauses the torrent after completed download.
I don´t want the whole program or system to shut down. Is this doable?

You don't do that there.

Settings -> Bittorrent -> Seeding limits -> When ratio reaches: 0.00
That's stop on download.

You can still seed like this if you right click and force start something.