After some testing, it seems like the output shows icons for the normal crafting table recipes, if i try to make a fence, it shows on the output but it wont let me grab the fences. And if i try a recipe from the custom table the icon wont show up, but if i try to grab it will craft the item.
I have been looking for the code that shows the output icon, but with no luck, anyone knows where can i find and change it?