Are you still interested in this? I’m working on almost the same problem right now, I dug a little deeper and found that there is an FInterpCurve C++ class that looks very similar to InterpCurve Float. This class has an “evaluate” method that should allow you to check the output of any input along the curve.
For the blueprints version the way I understand it now is that you create a couple points with an x&y value, add them to an array and make a curve out of them using the “make InterpCure Float” node. Then you should be able to evaluate in any point along that curve, however in the blueprints version there is no “evaluate” node, nor any way that I can find to do something with this new curve object.
I guess if you really needed it you could try to use the C++ class (which is what I’ll do next and report back) but it seems a bit mysterious why this ability to create curves in blueprints is added in the first place. I hope one of the Unreal devs can elaborate on this as there is no mention of it in the documentation either.