As it stands, if I want to swap an item on my hotbar with one in a container I have to move it to my inventory first and then open the container, swap, then close the container and add the new item to my hotbar.
I can't move it directly to the container. And I can't even move it to my inventory while I have the container open.
The same applies the other way around obviously.
It would be nice to be able to move item directly between hotbar and a container.