I am creating parts in the context of an assembly.

I lofted a right truncated cone between two concentric circles, but the shape was not quite what I wanted.

I saw no obvious candidate for a guide curve, so tried a centerline (Silomaster sketch 9 vertical on front plane thru origin).

Reading SW Help for loft with centerline suggested I click on the centerline parameter edit box then click on the centreline.

Well the centreline highlighted orange on mouseover, but clicking produced a message which makes no sense to me.

I tried dragging the green dots to straighten the (guide ?) line, and although the drag icon appeared on mouseover, the dots would not drag.

How should I proceed?