[***SPAM***] How to put a marker at exactly the center of a circle or rectangle?

When I draw a circle or a rectangle, then later I want to put a dot
(using MARKS menu item) exactly in the center of circle, etc...

Since I use very small grid size (2pt spacing) it is very hard to
visually count spaces in both directions so the dot shows up
exactly at center and also moving the mouse sometimes shifts
from the exact center also.

I looked at IPELETS->Align & Distribute but do not know how to
use this to do what I want.

Is there a better support for such operations? something
what will "highlight" the center or such will help, or
having a new menu shape, which is circle with dot for center in
it.

Thanks
--Nasser