Probably the easiest is to create a segmentation node and paint into it using Paint effect in segment editor (enable “Sphere brush”, “Edit in 3D views”, click “%” button to switch brush diameter setting to “mm” and set the desired size - e.g., 5mm). You can paint on 3D electrophysical map model and the points/strokes will be added to the segmentation (that is visible in 2D and can be shown in 3D by clicking “Show 3D”):
When you are done, use Mask volume effect to paste the segments into the volume (e.g., as very bright regions):
If the CyberKnife treatment planning system can load DICOM RT Structure Set or DICOM Segmentation Object then you don’t have to paste the targets into the volume but you can export the segmentation to a separate DICOM object.