Hi Len, what is it you are trying to accomplish by adding a point to the curve?

re:
> The only way I can find to split the curve is to trim it with a line.

The Trim command is the right tool to use for splitting an arc into 2 arc pieces.

If you want to cut it at a particular point you don't have to use a line, there is an "Add trim points" button that you can use to pick a splitting point on the curve.

- Michael