This mod adds a configurable HUD next to the hotbar, mirroring the off-hand slot. It will display whitelisted items from your inventory for easy viewing. It's intended use is for items such as the vanilla clock and compass, however you can add whatever you wish to the whitelist.
Documentation for the mod's configuration will be added in the near future. However, each configuration entry in the file has a description already, which should help to understand how it functions for the most part.
Bugs, suggestions, and crashes should be reported to the GitHub issue tracker.