Currently in WorkFront you are unable to edit a Cross-Project predecessors. If you want to edit a cross-project dependency you have to delete the dependency and then re-create a new dependency. It would be nice if we could edit cross-project dependencies.
Also, The pop-up window that appears when you create a cross project predecessor is locked. In other words, the "add cross-project predecessors" is unmovable and some data on that screen that would be useful to see.