Currently, to add more attribute icons, it is necessary to overwrite quark/attribute_tooltips.json, which means only 1 party can add icons at the same time. It would be nice if they were made extendable, like tags are.

Doesn't the attribute icon definition system work independently for each mod? I just tried adding an assets/quark/attribute_tooltips.json containing only a definition for botania:pixie_spawn_chance to Botania, and Quark kept showing its own icons in addition to the newly added Botania one.

I assume the issue is that this is actually part of a resource pack, not a data pack, since the client needs to know about it. They way it's currently initialized also unfortunately means you cannot redefine attributes, but resource packs should easily be able to replace existing icons and maybe even define new attributes.