Hopper Filter Item from the new Sift Dimension: Soul Shell/Casing/Capsule

A new item designed to allow the filtering of items using a single, configurable casing.

Once placed, it sits in an inventory slot and will never be passed on by hoppers, crafters, or droppers/dispensers. Instead, it is configured to a specific block or item and acts as a container for them when they are passed into that inventory slot. ​

I'm picturing a translucent, slot-sized shell containing a translucent icon of the item it has been configured to allow through.

Players could configure the shell using an anvil by placing the empty shell in one slot and the desired filter item in the other. ​

This would completely revolutionise sorting systems in the game, could enable filtering of un-stackable items, as well as improving Crafter use by allowing configuration of exactly where certain components need to go.

It makes it possible to build a filter using only one hopper while enabling all five slots to filter different items - saving space and resources for players and servers.

I think the unconfigured state shouldn't allow anything to pass so we can effectively disable slots in a hopper too.