(Only tested for Fabric 1.18.2) REI doesn't show the recipes of the shulkerbox because Minecraft uses a sort of special recipe function to keep the item's NBT data intact, and due to this, skipped from rendering by REI.
This Drag and Drop CT Script basically allows you to be able to see a recoloring recipe for shulkerboxes. Useful? arguably. Should you use it? only if you're used to see a recipe for everything craftable (Or in this case, Shulkerboxes)
