NBT Extractor
The NBT Extractor is the centerpiece of this add-on. It is a block that presents a graphical tree browser for any NBT-typed variable. Place the block, insert an NBT Variable Card into its left slot, and the block will load the full NBT tree of that variable so you can explore it. Once you have located the value you need, a single left click selects its path and lets you write it to an output card.