Curios API Mod 1.18.2/1.16.5/1.15.2 has Curios as a versatile and expandable accessory/equipment API for both users and developers. It offers functions to help these people solve various issues.

About Curios API Mod
It’s a project for the Forge mod loader. Besides, it currently provides a Fabric version.
It gives functionality for developers to supplement more accessory/equipment slots in a handy and compatible way.
Additionally, it shares with the user the possibility to configure those slots freely.
Curios add an inventory GUI only.
There’re only two items. They’re active through the creative Menu and mainly serve as examples for developers.
These are the highlights:
Expandable equipment slots through a central library
Easy to create and manage new slots through an identifier registry.
Merge the same identifiers to evade functional redundancies and generate the max compatibility to possible items.
Make slots on-demand
There are no slots at first. That decreases instances when there are one or more unessential slots.
Feasible to customize and manipulate slots
They own custom backgrounds, various sizes.
Through the API, developers can find functions to change.
Make item-curio relations flexible through the vanilla tag system
Categorize items into curio types as long as they have tags in suitable files.
Full integration with other inventory mechanics
Mending and Curses run with applicable stuff in the curio slots.
Obtainable from a single GUI
You can check extended equipment inventory GUIs. Developers can share their GUIs if necessary.
Curios API is a mod around armor, tools, and weapons. It requires Minecraft Forge.
Screenshots