Minecraft NBT Inventory Swapper is a tool that grants easy cross-world inventory swapping for minecraft.
I've always been using NBTExplorer to handle inventory transfer or swapping but it's kind of difficult. I saw someone requested for this, so I decided to make myself a tool that easily swaps inventory across worlds. I'm not intended to use the tool for cheating other than giving the ability to transfer your hard-worked items across worlds-- if needed.
Warning: Before swapping, please save and exit to title screen or close Minecraft!
2X Warning: If possible, please do backup your level.dat or <PlayerID>.dat, I've not thoroughly tested my tool, so there may be a chance that it will break your *.dat. On the safe side, I've hard-coded the tool to make sure there will be no problem swapping inventories.