not sure why my toolbars are not updated, i got this one loaded:
The buttons looked like this:
If i use the LMB Command, i get this:
Unknown command: 'UndoCPlane
When i change it as in your pic above and use it while drawing a line, it does not work:
Start of line ( BothSides Normal Angled Vertical FourPoint Bisector Perpendicular Tangent Extension ):
End of line ( BothSides ): '_CPlane
CPlane origin <0.000,0.000,0.000> ( All=No Curve Elevation Gumball Object Rotate Surface Through View World 3Point Undo Redo ): Undo
No CPlane to undo.
End of line ( BothSides ):
It works outside of a command though.