Longtime tipster Leonid Nemirovsky shares a method that allows quick segment creation in an AutoCAD polyline.
"If you highlight the straight segment of a polyline, select the middle grip until it is red, then press the Ctrl key, It will split the segment in two. If you right-click on the segment and press Ctrl again, it will convert the segment to an arc."
Notes from Cadalyst tip reviewer Brian Benton: This works in AutoCAD 2012 and up, as well as its verticals. Before 2012 you have to manually select the segment, hover over the midpoint grip to allow the menu to pop up, and click the Add Vertex options to split the segment. Do the same thing again, but pick the Convert to Arc option to make the line an arc.