[henri]

It would be useful to me to be able to have the start and due dates linked. For a given action, I'd like to be able to choose which of the two depends on the other.

So let's say I set it so that Due is one week after Start, then if I change Start to a day later, then Due would automatically be postponed by a day. For another action, I might decide that Start needs to be 4 days before Due. Then, if I change Due, Start would follow.