Set handle angle in degrees, and be able to lock the handle angle
Currently handles can be locked vertically or horizontally. This would enable you to lock a handle to any arbitrary angle.
We already calculate the existing angle to see if the point is flat vs. corner - so we thought we'd put the angle out as read only for reference, since we already have it.
Forcing a handle to remain at a certain angle while dragging is certainly possible - but it is extra work for the interaction. It also has to become a saved value as a property of the point, where as right now it's just a calculated value that isn't saved. That's why it hasn't happened yet :-)
Марсель Ишимбаев commented
This would be great! It is a mystery to me why hangles (pardon my french) are still read only.