Trinkets (Fabric) Mod

Trinkets is a trinket mod for Minecraft FabricMC. It allows you to add Trinkets to your player. Trinkets are alternate slots (similar to armour slots) that allow you to add alternate pieces of gear which can do things and that modders can take advantage of. It is similar to Curios API, however, it is a bit simpler and more in line with Vanilla but a little less compact and without the default slots and example trinkets. By themselves, trinkets do not do anything but instead require mods to make use of it and come up with trinkets and a lot of trinkets may not look this good.

An example is the Charm of Undying mod which adds a custom slot for its mod which allows users to add the totem of undying while treeing the offhand from the totem of undying.

Existing vanilla items can also be turned into Trinkets and be given their own abilities, such as in the Charm of Undying  mod, and the items can have descriptions.

Trinkets are officially only for FabricMC, Curios API is arguably a better mod if the mods support it and has recently been ported to Fabric, though is not on many older versions for Fabric.