Describe the feature

I alread said in discord :P Make Item#getCloneItemStack() return filled tank instead of giving empty tank.

Reasons why it should be considered

It makes testing in creative much easier and good qol update in general.

Additional details

No response

Actually, as ChiefArug pointed out on discord, there's no need for this 😃

Just hold Ctrl while middle-clicking to copy the block along with its block entity NBT (standard vanilla functionality).

Leaving open for now, it seems Ctrl-middle-click copies an item that looks full, but doesn't provide a correct item fluid capability.