If you try to add an extra port redirection to a currently running tunnel you can add it but not save the changes.
1. Create a tunnel
2. Start the tunnel
3. Click on "properties"
4. Within "Port redirection" Add, Edit or delete an item
5. You cannot save the edited item as the OK button is greyed out.
A warning stating that you cannot edit a running tunnel would be a welcome addition. :)
Stopping the tunnel and then editing it works fine.