No Longer Supported, I recommend Modrinth's ItemSwapper mod, it's very vanilla-like and works better.

Tool Swap allows you to switch items in your hotbar with your inventory. You can also switch items in your hotbar with your Ender Chest, but only if you have one in your inventory, are standing near an Ender Chest, or if there's an Ender Chest item nearby. You can use the following trigger for different actions:

Ender Chest Required

• "/trigger swap_tools": Rotate your selected item with the first 3 slots of your Ender Chest.
• "/trigger swap_hotbar_with_ender_chest": Swap your hotbar with the top row of your Ender Chest.
• "/trigger rotate_hotbar_with_ender_chest": Rotates your hotbar and Ender Chest rows downward, with the hotbar row becoming the top row.
• "/trigger swap_selected_with_ender_chest": Swap your selected item with the matching slot in the top row of your Ender Chest.

Inventory Only

• "/trigger swap_hotbar_with_inventory": Swap your hotbar with the top row of the inventory.
• "/trigger rotate_hotbar_with_inventory": Rotates your hotbar and inventory rows downward, with the hotbar becoming the top row.
• "/trigger swap_selected_with_inventory": Swap your selected item with the matching slot in the top row of your inventory.

Tip: You can open the chat then press the up arrow to bring up the last used command.