Learn about Insert Elements Mode in respective chapter.
End of Segment command inserts partition line into column or appliqué, dividing it into so called segments. One point of the new segment end line is the selected node and the other point is found automatically on the opposite side (the nearest node).
Segment ends serve to define stitch direction inside column or appliqué. When generating stitches for columns and appliqués, program takes into account direction of segment end lines and conforms stitches direction on those places.
End of segment - effect on column stitch directions.