While ties are set to be toggle-able, I found that slurs are not. I'm not sure if this is on purpose but I figure that slurs should also be toggle-able. For now, highlighting two notes to be slurred and pressing "S" will only add slurs, even stacking them when one already exists. Ideally, slurs should alternate to appear and disappear as a user activates the command. I hope someone knows what I'm going at; I don't know what the technical term for this feature would be. Perhaps someone can implement this as an improvement?