Is it possible to alter the size of the carving tool in the CNC section of Luban?

Is it possible to alter the size of the carving tool in the CNC section of Luban?

I ask because after selecting the CNC tool to use (flat end mill), then selecting use other bit to find the box to enter the new size, the size box appears and a new bit size can be entered.

At the same time the ‘V’ bit is highlighted even though the flat end mill bit was selected initially. As for the persistence of the selected parameters, surely they should stay regrdless of the selected values. Once again, help from any knowledgeable person would be9