funcy's PerWorldInventory [1.21+]

This minimal Spigot plugin gives each world-group its own saved state (inventory, armor, offhand, ender chest, XP, health, hunger, saturation, potion effects, gamemode, and optionally location). Multiple worlds can be linked to share the same inventory by putting them in the same group. Data auto‑saves on world change, quit, and on a repeating timer.

If you want a live demo, try it on my server: 198.50.158.122:25618