No documentation on how to add data tags to custom items materials.

[Millymilo000]

I'm using this plugin on Minecraft 1.8.8, and I want to add a custom item that includes all "double_plant" blocks (Sunflower, Lilac, Double Tallgrass etc.) which would require me to specify the data id for each double_plant (Sunflower has data id of 0, Lilac has 1 Double Tallgrass has 2. ) When I try to add the Lilac I tried DOUBLE_PLANT,1/1 DOUBLE_PLANT/1 DOUBLE_PLANT,1 and many other things (I tried those since that's similar to how the Coffee recipe does to get cocoa beans.) But unfortunately none worked, I always got a error saying that "Unknown Material:" or "Item Amount can not be specified for Custom Items"

So I'd like some documentation on how, or if this isn't even a feature, I'd love for it to be added as one.