We have smoothing use the orange user defined edges to give the user some control over smoothing. You don't always want to use all triangle edges. I think both are useful, so we should have a way of doing both. Probably the Smooth
button will have with a little triangle that shows a popup menu, allowing you to change the function and label of the button. We don't yet have this kind of UI control yet in other areas in Spine.
I've added an issue to track it:
EsotericSoftware/spine-editor740