That will be in the next build, but until then there's an easy way to do it:
I presume you are talking about control points in the target window (since the source window isn't georeferenced and thus does not yet have sensible coordinates to speak of...).
1. In the target window, place all the control points with the mouse.
2. Save those control points.
3. Open the saved control points drawing.
4. Use the usual drawing editing methods (alt-click a point, etc.) to pick each point and then set the precise coordinates you want for it in the Coordinates tab of the Info pane.
5. Back in the target window, load the saved control points drawing. All the control points now are precisely where you put them in step 4.