phudge, there's a macro provided with SE that does that. It is located in Program Files\Solid Edge\Custom\nSidePolygon.
You can create a new toolbar button and attribute it to the macro. It takes some time for it to load, it's not as fast as a regular tool.
Personaly I prefer to do it the manual way. From the look of your screen capture, I think I'm doing it the same way as you.
- Start with a circle, convert it to a construction element
- Draw contiguous lines and taking care always "snaping" the endpoints to the circle. The polygon is inscribed within the circle.
- Assign equal relationships to all the line segments
- Dimension either the circle or a line segment, position the circle to the origin so the polygon is fully constrained.