You can now set an item’s NBT from the creation GUI! Whenever you set the item in the GUI to something that has custom NBT, it will automatically be set under the “item.nbt” key in the item yml file!

As a side note, I have very limited internet access right now — just enough to upload occasional updates — and likely won’t be able to respond to any PMs for about a week. I’ll respond to them as soon as I can, though!