Swap UI can be activated by shift. Then you can select items using up / down arrow button, or mouse scrolling.
For Quiver, the UI will appear when you hold a bow, and you will shoot the selected arrow.
For Tool Swap and Armor Swap, you need to press R to swap the item.
Ender Backpackl2backpack:ender_backpackAnd you can put Quick Swap items in your ender backpacks. Swaps can trigger inside ender backpack as well. Keeping swaps in your ender backpack allows you to not lose precious weapons and gears in swaps when killed.