In version 18.104.22.168, I noticed that I had a few extra attributes for an entity. Upon further investigation I discovered that these attributes were the result of relationships that I thought I had deleted. Further, I discovered that the model contained a number of entities that I thought I had deleted. These relationships and entities were not visible in the diagram.
I suppose it’s a feature that I can have things that are in the model, but not visible on a diagram. However, if I can add things to the model via the diagram, I ought to be able to delete them through the diagram as well and I cannot find a way to do that. Perhaps, the delete key should trigger a dialog that asks whether you want to delete the item from the diagram or the model or perhaps the context menu that pops up when you right click on an item should include a Delete From Model entry or perhaps both.