I totally agree on the need for a jump-list of all entities of a given type.
The alternative is having the entities as always listed in the App, which means that they take up a lot of space, or having to create a table view just for this purpose.
Perhaps a right click on the App name/icon could show the diagram of all app types (inc their relations) and then a click on the name of a specific type brings up a lift of all entities of that type.
Or if you already have an entity open, clicking on the name of the type (in the header ribbon) brings up a list of all entities of the same type.
Is that the kind of thing that would suit you @B_Sp?