This mod adds the Artisan Replicator, A block crated with endgame materials that gives you access to duplication. It acts like a furnace, But instead of consuming the input and crafting an item, It inserts a copy in the output slot, and the item is not consumed.
(Yes, you could hypothetically just put coal in the dupe slot, but that's no fun. Plus, the thing about this mod is "easy duping," so I didn't want to go too crazy on balancing).
Here's the layout of the replicator:

The lights on the bottom of each slot will glow if items are input correctly, and the machine will start. The bar in the middle will show the progress of the current item. When finished, your duplicated item will be provided in the 3rd slot.
The purple button in the UI can be spam-clicked to speed up the meter.



Boosters can also be crafted to speed up the duplication process. There are three levels, and each goes faster the higher you go.
Just in case you don't have JEI, here's the recipe.


"Why make this mod?"
Because I'm lazy and there aren't that many 1.21.1 Duplication Mods yet. "Be the change you want to see in the world".