One suggestion: Would it be possible to make sublayers within each layer?

I mean, if for example in a window that are "blocks" in that same window that have other subwindows in which to name for example "Dirts", "Stone", etc.
I think it's a good idea to implement that option if possible

Sub Categories would require a massive rewrite of GUIShop which unfortunately I do not have the time for. I have marked this down on my todo, however I wouldn't expect to see it soon.