I would love a way to define a particle for a given GUI - one possible idea I had was a JSON schema that maps a GUI classpath to a texture, for example:

{
  "gui": "org.violetmoon.quark.addons.oddities.client.screen.BackpackInventoryScreen",
  "texture": "quark:textures/misc/backpack_gui.png"
}

Alternatively, texture could be a particle, however I believe that would require code registration of a new particle? Which you wouldn't be able to do easily if you were a modpack developer working only with assets and data.

Additionally, a code-based API for mods would be neat too, allowing them to register custom rendering for a particle

Went down a deep rabbithole where I was initially planning a feature close to this, then I had a breakthrough with another method.

The release thats about to come out will make this not required, it should magically just work for all guis including modded. https://bsky.app/profile/corosus.bsky.social/post/3lfftzwzblc2w

There might be some rare cases where I'll have to add custom support for mods that go extra crazy with special screen rendering code, like xaeros minimap, but otherwise 99%? of cases it should just work.