How do I stack "unstackable" items

Some items such as keys and powders I have gotten aren't able to be stacked and that ruins the organized chests I have. Is there any way to make them stackable? I have tried relogging and everything.

 

This doesn't work for all items, but you can put the items that aren't stacking into your inventory and then use /lobby to switch to another world. Items usually stack after that.

 

Throw both stacks onto the ground for a few seconds. Can sometimes take a few tries.