By default, heads down display hides the hotbar when not in use and the arms when they are not holding anything; both can be configured in various ways. The arms can be configured to be hidden while holding an item, while not holding anything, while swinging, while not swinging and always.
Heads down display is configurable via a file named "headsdowndisplay.toml" in the "config" subdirectory of the Minecraft directory and a graphical user interface (GUI) when Mod Menu is present.
默认情况下，不使用物品快捷栏时会自动隐藏，当更换物品时才会显示，也会把空的手隐藏掉，这些都可以在配置中自定义。
Downloads
Embedded Library：Cloth Config API (Fabric)
感觉这个模组会增加一些游戏体验