ActionBar Extension&Swapper by MasterBit

Add two swap keys, left and right. Also add up to 18 additional swap keys to load single slot-items into the hotbar. There is also a preview key, by default set to left alt: it shows on screen the custom keys item-slots with the key binding associated (just use it, it's very simple to understand). Finally you can customize the keys in the controls menu of minecraft vanilla, and customize the mod settings in the config file named <actionbar_extension_mod.cfg>