I am having a hard time selecting a center node and moving it from it's default position.
I am making an arc shaped label with degree marks. I draw the the first mark using a rectangle. the rectangle has a default center node. I will use the Transform > Rotate to make a more degree marks. To do that I want to move the center node of the rectangle to the center of the arc. I am having a hard time grabbing the center node to move it to where I want. I've done it before and I assume there is some sequence of selection clicks on the node that allows it to be moved.
You might already know this, but I'm not completely sure what you mean when you write, "center node", so...
There is a Center for the shape, but that's not what you want to move. You want to move the center of rotation.
The center of rotation (circle with a dot in the center) is visible when the shape is in rotate/skew mode.