Click Center Line
in the Dress-up toolbar (Axis and Threads sub-toolbar).


Select the circle or the ellipse to which you want to
apply the center lines.
Center lines are automatically applied.
.

Click in the drawing to confirm the creation.
Optional: To modify the center lines, you can select
them and use the manipulators.
Note:
When creating a center line on a generative view,
a message will be displayed if the center line cannot be associative
to the 3D.