Mike Hope got a reaction from Davey in EOSHD Pro Color for Sony Cameras
Sorry for the late reply. Didn't read the rest of the thread, so maybe this was already answered by someone else.
I just missed the point that you have to use the SET option at the very bottom of the list (below the C1-3 settings) to achieve the WB K and then store the K value to one of the Custom slots.
Inside the Custom 1-3 you cannot alter the K value, you can only alter the shift (A-B and G-M).