The Selected polyline(s) right-click option "select contained terrain vertices" seems to be non-functional.
In "normal" Visitor 4, the terrain vertices are shown as "selected", the mouse pointer changes to the "Terrain Tool Pointer" and the Properties Window Contents changes from displaying the Polyline(s) properties to the Terrain Properties info, where the selected vertices can be subsequently adjusted via the usual Terrain Properties Window options, level, smooth, set to average height, etc.

This is a hugely useful option for selecting terrain areas via polyline/polygon for subsequent smoothing/levelling operations... it would be terrific to see it enabled!