Mods -> NeoForge -> Client settings -> NeoForge Light PipelinePackages adds packages, which can hold 8 stacks of one item.
The catch: Packages only hold 8 stacks. There are no storage upgrades. The size is not configurable. But packages can nest inside each other, and even stack when they contain the same contents!
Other than their size, Packages behave like cheap shulker boxes. Measure with a comparator, crush with a piston, and dispense with a dispenser; shulker box loader and unloader designs work great on Packages.

Kat came up with the Package Crafter model, unascribed came up with the idea for bundle interactions.
See the minisite for more documentation.
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