Mike Hayes wrote

The Create Polyline from Existing Segments tool works perfectly well.

Mike Hayes wrote

But after the individual line segments have been successfully converted into a polyline, it is not immediately obvious to the user that anything has actually happened because everything looks exactly the same as it did before and the Command Line continues to prompt the user to choose another segment.

I think it would be helpful to give the user some feedback to confirm that a polyline has been successfully created. Perhaps this could be done either by highlighting the new polyline or by displaying a message in the Command Line.

Mike