This is an interesting idea. I have an extension (currently non-public, so please don't look) that automatically adds all ORM elements that do not have a corresponding shape to a designated group. The extension provides one model error if there are any current (shapeless) items in the group, and the items can be dragged directly out of the expanded group to create shapes on the diagram.
This request is similar but a little more complicated because it provides a more complicated context to determine when a shape is 'missing'. One way to interpret your question is 'given one or more diagrams and a list of object types, tell me when one of those object types or any fact type associated with them has no corresponding shape on the designated diagrams'. The proposed extension would allow you to associate one or more diagrams with a group, and then pick object types you want to track for that set of diagrams. If new fact types were added for any of those object types, then they would automatically appear in your group and you would get a model validation error. Double-clicking the error would automatically activate the (first) diagram if needed, then expand the group in the model browser, allowing you to place new fact type shapes directly where they are most aesthetically pleasing. You could also choose to explicitly exclude the shapeless item (you would still see it in the group, but it would no longer give you a validation error).
Obviously, this is a little more complicated than Visio's expand command, but it also gives you live tracking in the model, so you can formally record your intent to show all fact types for a given model on a diagram, and have the tool tell you when the intent is violated. It is also a refinement of the more general notion of the lack of a shape on any diagram, which I already have code for (an advantage, at least for me).
Please comment on design. I can't give you any schedule on this right now, but if I can get design feedback then it is there to refer back to.