Can't select transparency on leaves

When I use the 'Leaves' block base preset, for some reason, MCreator disables the ability to enable 'transparent parts' on the block. When I load into the game, the leaves are solid colored no matter my graphics settings. I cannot select transparent parts or what type of transparency the object has, as they are just grayed out. Does anybody know if this is a bug or if there is a solution? I'm still very new to modding so I'd prefer if somebody gave a solution without using any raw scri