They should exist, they don't.
CRB pg. 130: "New spells, rituals, or alchemical preparations can be learned by studying spell formulae or finding some mentor (either a spirit or another Awakened individual) to teach you".
Whether by chance or intent though, every Ritual except one in the CRB aligns with one of the spell categories, even though some don't outright say so, and none of them are officially categorized into spell categories.
Combat Spell Formula - Prodigal Spell
Detection Spell Formula - Remote Sensing
Illusion Spell Formula - Curse
Health Spell Formula - Circle of Healing
Manipulation Spell Formula - Circle of Protection, Renascence, Ward
Watcher -
? Hey diddy hoe diddy, no one knows.
