For some reason, SOME of the dlc I own isn't saved to the 'outfits' section. BUT I do have the costume pieces, so I can just make the costumes and save them,
LittleBigPlanet 3 launching November 18, pre-orders net costumes and plushies | Engadget
LittleBigPlanet 3 gets MGSV: The Phantom Pain costume pack - Metal Gear Informer
Most LittleBigPlanet costume DLC to become cross-platform, only require one purchase
These New LittleBigPlanet 3 Costumes Are Just the Best | Push Square
LittleBigPlanet 3 - Monsters, Inc. Costume Pack DLC! - YouTube
LittleBigPlanet™ 2 Bioshock Costume Pack
LittleBigPlanet's Marvel DLC to be pulled from PlayStation Store - Polygon
Downloadable Content/LittleBigPlanet 3 | LittleBigPlanet Wiki | Fandom