1.20.5+

A simple, lightweight Minecraft datapack that allows shulker boxes to stack up to 64.
Shulker boxes will stack in your inventory, on the ground, and inside hoppers, etc. if they have the same color and same items, unless:
 
1. The item was created before this datapack was installed
2. The item was not obtained through crafting or mining (i.e. creative inventory or commands)

These issues can be easily solved by placing and re-breaking the box.
This datapack does not use functions or any kind of hacks, so it won't hurt performance at all.

Uninstalling:Remove the datapack from your datapacks folder. Any stackable items will remain stackable until you place and re-break them.