Comment 3 for bug 217029

I like that idea too, although Ctrl is used already to snap at angles.

Shift might be a good option, now it is used to rotate both handles simultaneously but smooth nodes handles always do that. Using Shift also makes sense as its equivalent to controlling handles while drawing with Bezier tool (drawing a cusp node).

It might be nice to have Shift as a modifier on smooth nodes handles that turns them into cusp.