EditorSceneManager.SaveCurrentModifiedScenesIfUserWantsTo() creates a confirmation window : 
The problem is the windows has 3 buttons but it only returns True/False
Save : True
Don’t Save : True
Cancel : False
But this doesn’t make any sense. I want to know if the user wants to save the scene but clicking " Don’t save " will actually return TRUE. This window should return an enum with 3 possibilities. Anyone know a workaround?
The scriptref for EditorSceneManager.SaveCurrentModifiedScenesIfUserWantsTo has been documented to describe the Save/Don’t Save as true and Cancel as false. It’s more detailed than the current docs.
Dealing with the same problem. Does anybody have an update on this issue?
[Edit] Nevermind. After a bit more digging, I see that the scene save functionality happens on its own, we don’t have to implement it. So Save returns true and the scenes are automatically saved. Don’t save returns true, but the modified scenes remain unsaved. Cancel returns false meaning the user wants to cancel the operation completely. I get it now.