This AppleScript and corresponding Python script calculate a number of points in a circle given that circle's center and radius, and paste those points into OmniGraphSketcher using system events. The default number of points is 36, and can be changed by editing the variable "segments" in line 22 of circle.py.
To add as a toolbar button in OmniGraphSketcher, place the entire Circle folder in the directory ~/Library/Scripts/Applications/OmniGraphSketcher/ (where ~ is your user directory), then add the button using View > Customize Toolbar...
The the .scpt and .py files must be in the same directory for the script to work. Feedback is welcome; please email OmniGraphSketcher@omnigroup.com with your questions or concerns.
Download the .zip