This mod changes the way that quickbar swapping works. It only works in combination with mods that allow for extending the amount of quickbars beyond 2.
It changes the behavior of quickbar swapping (default key: X) from rotating (every quickbar moves one row up), to swapping a pair of bars.
By default the keybindings are X to swap the bars in the current pair, and SHIFT + X to rotate to the next pair.
See the mod portal for more information.