A little late, don´t know if you found a solution for your request yet.
But when I was searching for a list of bone names in Advanced BoneMod I found this: "
You gotta go to advanced bone mod settings in the char maker (right side, one of the four options). There you look for the "dan_s" bone. There you can adjust the x,y,z scale. Works with futa characters as well."
This bone affects dong and balls simultaneously, it works as you can see here
View attachment 1651736
The bone cm_J_dan_f_top do the same, cm_J_dan100_00 affects only dong.