Actually, while I'm commenting on this (and having a better look now that I've worked out how to find it), there's a couple other things. When items have multiple recipes, the tree only shows one option. While it may be tough to do otherwise in the tree itself, but when you highlight that item, would it be possible to show all the recipes that make that item below?
Example:
Bronze Hatchet.
The recipe for the second item (
Animal Glue) shows the hardest of the three recipes to make it (Bone Ash only seems to come from grade 4 mining spots). Even when you highlight it, the more detailed recipe for that item that comes up below is the same one, and doesn't mention the other two recipes for it.
Here's a couple other things you may or may not want to, or be able to add (although I know you can do anything):
Just in case anything isn't obvious, black numbers are the number of that item required in the recipe, coloured numbers are crystals required, and the number on the green arrows shows that there are other versions of that recipe. Clicking on that little green logo would cycle through the different recipes for that item, and populate the recipe tree with them. Oh, and the bold red number 1 next to bronze ingot represents 1 crystal, as opposed to shards.
Here's another one without the crystals, as I think they make it a little too cluttered, and probably wouldn't be as helpful as the other two things: