Comment 2 for bug 1783444

I think case (4) is a red herring. It's like showing a dialog of all undoable actions on a document and asking which ones you want to save.

If you really need to save only some libraries, then use the Component Tree to either Revert those you don't want changed, or Save those that you do.

This dialog should just be the standard Save / Discard / Cancel dialog.