Setting this item duplication up is pretty easy. To replicate it all you need is:
-Sophisticated backpack
-Stack upgrade for said backpack (Any should work I imagine)
-More than one bundle (the minecraft one)

Afterwards if you sort your backpack all of the bundles will go inside of one inventory slot (whatever the size is on the stack upgrade is how many will stack in each inventory slot) allowing you to put an item in all of the bundles in the slot. If you spread the bundles into different inventory slots each bundle will now carry the item you put inside of it.

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I used a block of allthemodium x1 here. I started with only 2 allthemodium nuggets and was able to get this in no time.

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

I can confirm this is a bug and I can duplicate items with it.

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.