I always find it hard to get the segment I want to extract as switching seems to be only possible in viewport by moving the mouse around. often results seem inconsistent, imho.
why not use ALT to toggle and/or add a menu option “toggle”
yep. sorry, I was a bit imprecise. I mean mainly closed curves; but sometimes when it is a complex 3dSpline also non closed curves do not behave ideally: basically I would prefer to choose the direction from split point once and the command to remember until completed. right now if you get close to the other part of the curve in the viewport it switches.
It would be cool if Tab direction lock could be expanded to work in a situation like this. I suspect that is not an easy thing to do but it seems the most natural, UI wise, to me.