You do not add accounts. Once a connection is up, Tradeus asks the broker which accounts it holds and lists them underneath. The connection has a status, and so does each account below it.
Connected
The session is up and orders route.
Session closed
The connection exists but its session has dropped. Reconnect from the same row.
Disconnected
Not connected. Nothing routes.
Authorization expired
OAuth only. Re-authorize from the row.
Closed
The broker no longer lists this account — an evaluation that ended, usually. History stays in the journal.
Each connection also carries a Flatten all button, which closes everything open on it at market. It is deliberately at the connection level and deliberately not hidden behind a menu.
A dropped session does not pause your strategies — it just means their orders have nowhere to go. If you have armed locks, read When a lock cannot see, because a disconnected broker also means an unenforced limit.