Why can I not edit the synchronization user or the project key (on the edit connection dialog)?
The backbone configuration heavily depends on the project which is being integrated. Changing the project would most likely break the synchronization. Also changing the project would result in other issues to be synchronized. We might allow to change the project key in the future.
Backbone uses the synchronization user not only for authentication but also for distinguishing which changes should be synchronized to the other project and which changes have been performed by Backbone itself. Changing the user would imply that all changes by the previous synchronization user would now be recognized as user changes which have to be synchronized.