Class diagram: Option to show missing classes, associations
As a modeler, when I drag classes and associations from one diagram to a new diagram, I would like to be able to add/show a missing class when I select an association, and a missing association when I select a class.
Currently, when you drag classes and associations from one class diagram to another, the edges can all point to a missing dependency, but there's no indication of what the dependency is or easy way to add it. For example, if Elm is a Tree and Oak is a Tree, and you drag Elm, Oak, and their associations to a new diagram, the associations will both point to the invisible Tree class; however, there's no indication what the missing class is. The editor knows what the missing class is, so if it maybe showed it as a tool-tip over the association, or if there were a right-click menu option to "Show missing classes," it would save a trip back to the source model to figure out what is missing. This is more important for large/complicated models.