I dont think this exists,
I am sure we have all experienced the fact that when picking rails or curves for sweeps or networkSrf, we find ourselves having to duplicate curves and join or trim/split them to get a dedicated set just for the one surface, a model with one curve per surface edge soon becomes a model with three or more curves, each one suited to a particular surface.
It also leads to moving up and down a list until the particular curve we need shows up,and with the highglighted curve being 1 pixel its sometimes tricky to see a difference between one and another choice.
What if the command said…select curves (plural !!!) for first rail, then hit enter, then select curves for second rail, then hit enter, rhino joining them together in a virtual way to use them for the rails. We could cut up the curves beforehand and have just one curve still as originally created, rather than have to duplicate curves and edit to create a set per surface.