As a user, I need to be able to move leaf nodes from one branch to another branch.
So, for a tree data structure, my initial state:
Item 1
subItem A
subItem B
subItem C
Item 2
subItem X
subItem Y
subItem Z
I then drag 'subItem Y' from Item 2 to Item 1:
Item 1
subItem A
subItem B
subItem Y
subItem C
Item 2
subItem X
subItem Z