Available from Builder 1.60.16.18 or higher.
IMPORTANT: It is necessary to have a vertex at the most extreme point of the arc, as described below:
To create a semicircle in Builder Parts:
1. In Geometry, select Build Circular Geometry, and draw the circle of the desired size.
2. Right-click on the created geometry and select Create Part with Builder Parts from the selected geometry/composition.
3. Select the Top or Bottom Angle until a straight line is formed.
4. Add a vertex to the remaining angle (bottom or top).
5. Delete the overlapping vertices as the drawing will not be validated.
6. Click OK to finish.
7. Replace the selected geometry with the new geometry.
Example