Currently it is possible to add connectors between shapes but it is not possible to annotate them. We are adding text notes to each connector but they do not move once you move shape. Please add "sticky" titles to connectors.

The ability to label connectors would help alot with keeping things straight

This would be awesome if you add connector to a decision node and need to label the connector as positive or negative decision path.

Add the ability to add text over connectors.