Thanks for the great application. I would like to suggest possible improvements.
1-Adding "pick point" feature would be great to "hatching" tool just like autocad. Even maybe a "boundary" drawing.
2-When two objects, say two circles away from each other, are joined by "Round" property, it should create a closed contour.
3-In "trimming", limiting entity could be multiple, and after choosing limiting entity, the part you choose should be the part to be trimmed.