Torrents in transmission can’t be deleted
Torrents in transmission never really go away, and will self-populate after a restart of Freedombox or transmission app.
How to replicate
Add a torrent to Transmission. Download it.
Delete the torrent (right click, and select “delete torrent with data”)
At this point the data is deleted from storage and the torrent left the list.
Restart transmission (in freedombox/plinth/apps by toggling the app, or by restarting the whole freedombox)
Check transmission - the torrent has returned, and probably started downloading again.
Set defaults so deleted torrents stay deleted.