Select a non closed linestring
right click and select profile viewer
If the line has an elevation you will see the line in a profile view
right click and select surfaces
turn on the desired surfaces
Don't erase the line in the profile view, it is your linestring and hence what you see in plan view will also be deleted.
If you want to do more than just view the profile you will need to create an alignment. The alignment object type creates a container for the referenced surfaces and objects that you draw. Lines in the plan view can be used to create the HAL and if its 3D the VAL. Other lines from the profile view can be used to create the VAL. You can have multiple profiles for any one HAL. You can then draw other objects in the profile view of the alignment and add text.
tim