How to Make a Curve/Surface Along Side an Existing Wall

I want to make a curve along side an existing wall I made by VisualARQ, can I do it with some tools in Rhino that similar to the Auto-Select/Grab in Revit? I want to make the curve on the wall and extruding it out so it looks like a platform.

not fully sure if i understood you correct but you can use the command ยดRibbon for a surface and Slab in case you need that curve solid or Fin might do either if its a curve which has to be extruded normal along any surface

Hi Eve - one way would be to Project a curve onto the wall. Its hard to say without the object.