In FFGs rulebooks and fiction several Schools and Titles have been mentioned that do not yet have a write-up.

Crab Clan: none

Crane Clan: Daidoji Harrier, Doji Rhetoritician, Kakita Artisan. Titles: Elite Royal Guard

Dragon Clan: none

Lion Clan: Matsu Beastmaster. Titles: Kensai, Deathseeker

Phoenix Clan: Izawa Ishiken (Void Adept). Titles: Elemental Adept

Scorpion Clan: Titles: Kagenari (Master of Shadows)

Unicorn Clan: Titles: White Guard

Generic titles: Abbot, Sensei

Are there any Schools and Titles I have forgotten? Any from earlier editions that need s to be updated?

There is the Bayushi Elite Guard mentioned in The World, A Stage - I suspect they would be a title rather than school, since they're not 'trained from gempukku' individuals but rather picked to join it once recognised as awesome (Bayushi Shoju picking their new commander personally in that story)

I think the Elite Royal Guard of the Crane was always specifically the 'Empress' Guard' - whilst they might nominally protect any royal family member, they were legally speaking there to protect the (almost always Doji-born) Empress and/or Empress Dowager, since there was a historical precedent for that with Doji Haranobu right back at the birth of the Empire.