Even when I get a connection lost or reset (sorry I did not copy the exact wording and/or error code),
either from a sql sheet or from trying to expand a left-hand tree node, I am not being offered the option to reconnect
(which remains greyed out).
This has been a nagging problem with sqldeveloper *forever*.
A keep-alive or ping interval should perhaps become a new parameter when defining a connection.
Not everyone has clean, permanent connections (e.g when working over a VPN).