I've successfully used it to edit many featurelines. My situation was that I had an existing curb return, surveyed every two feet. So the featureline for that curb return was composed of many short, straight segments.
I drew a new featureline for the proposed curb return, which was usually a tangent, then an arc, then another tangent. And it was not coincident with the existing curb return, it was offset by some distance, and that distance varied along the featureline. So most definitely not parallel to the existing featureline.
I used the 'elevation by reference' button to set the proposed featureline elevations to match the existing featureline elevations. I added a few extra PI's to the proposed featureline at the quarter-deltas, so it would more closely follow the existing grade.
This worked well to model nine intersections along a 2-mile corridor.