I noticed that when I have an element in my workspace and it have a custom model (3D model), I cannot open element for change something. I hope that is only a bug in my Worskpace, but I give you my workspace. I suggest you to try with Dragonium Pickaxe, Dragonium Bow, Dragonium Hoe and Dragonium Sword ( you can also try with other things, because each ,element that I cann't open, has or had a custom model (3D). We can delete element and recreate it and after it work.
P-S : We cannot double clicks or click on buton "Edit selected mod element"