Hi blenddooler - the equivalent of this in MoI is Edit/Trim.

Select your curve you want to cut into pieces. Now run Edit/Trim.

At this point, you can either select any other objects that you want to slice the curve with, or push the "Add trim points" in the options area, which will let you pick slicing points on the curve with your mouse.

When you have finished picking cutting points push "Done" (or push enter or right-click in a viewport).

Then there is one more stage - this is where you pick which pieces you want to discard or keep. If you want to keep everything, push "Done" (or enter/right-click) and all pieces will be kept which is the equivalent of Rhino's Split command.

- Michael