Hatter remembers which hats and cloaks should be visible when equipped, and which should be hidden.
When you're wearing a hat or a cloak, Hatter will check if you currently have it shown (as set in Interface -> Display). The next time you equip that item, Hatter will automatically show or hide it based on your remembered preference.
New hats and cloaks are shown by default. This can be changed so that new equipment is hidden, or this feature can be turned off so that unrecognized equipment inherits visibility from the current setting.
Hatter's predecessor is a (less complete) Weakaura. If you'd prefer installing through WeakAuras, and don't mind missing features (profile support, config, viewing/clearing stored items), then you can find it here on Wago. Do not use both the addon and WeakAura. If this addon notices that the Hatter WeakAura is active, it will offer to disable the WeakAura to avoid conflicts.
Check out the Localization section if you're interested in helping to translate this addon.