Hello I just want trinkets have transparency (or be hidden).
Show Me Your Skin! mod already offer this feature for armors, shield and elytra.
I don't think the developer of mod can do that, as they said:

Compatibility with "trinket-like" mods like Travelers Backpack is mostly out of scope for this mod, so I most wont be working on this.
(enjarai/show-me-your-skin#52)

thx.

Trinkets doesn't do rendering itself, so it can't add this feature.