I just had a quick look at the core tunnel alpha. The few configs I’ve tested as well as ECDSA keys are working fine.
While creating an entry a few things popped out:
Missing (guess due to alpha state?)
The [TAB]-order of the “Forwarding” table doesn’t proceed to the next line. That would be helpful.
Identity file selection now with an additional file dialog for every entry instead of a dropdown box. I prefer a centralized view/tab/panel for the configuration of the private keys (like SSH Tunnel did in it’s global preferences tab). The Keychain and password info columns there were also useful at times.
I like the optional full-path-info for the used key in the advanced config tab and with “Equivalent Command” (which is great for testing, thanks)
I’d really like to see which key is used in the host overview pane instead of the static string “publickey” next to “Authentication” (filename with optional full path maybe?)
A one-click-backup or “sync config in <folder>” feature
An autocomplete feature, which parses an existing .ssh/config for details while creating a new Tunnel and fills out what is known from the file. (cyberduck does does a great job at that)
A way to import already existing host configs from ~/.ssh/config. Or even some sort of selective sync mode, so one doesn’t have to update the tunnel entry when the corresponding entry in ~/.ssh/config changes.