Hi Brian, yes if it's a line or arc being resized it will look through other open curves and if there is one that has a shared endpoint with the one being resized it will use the shared endpoint as the scale origin. If each end is touching something else it will target the end that was nearest to the selection click point.

Otherwise if there isn't any other curve touching it, it will use the midpoint as the scale origin.

- Michael

Thank you Michael.

So to place a helper line perpendicular to base line, and beginning (or ending) at the base line, I can add a 3rd temporary anchor line, (or curve), beginning at the intersection spot of the base line and helper line.
And then re-size the helper line, by selecting it near the anchored end, just in case the other end happens to end at a 4th line, (or curve), end.

- Brian