After Duplicate and Retarget, the new character has its own animation library, but its gameplay Blueprints, Anim Blueprint defaults, DataTable rows and soft references still point at the old character’s animations.
The engine’s two options do not fit that job. ReplaceReferredAnimationsInBlueprint only remaps Anim Blueprints, and Replace References is global, so it would also move the old character, which has to keep its own library.
Retarget Relinker is an editor commandlet (RRL) that rewrites references only inside the folder you name, and only to twins it can prove: same class, old asset on the old skeleton, twin on the new one, no two old assets predicting the same twin. It reads skeletons from registry tags without loading animations, refuses anything that still drives the old skeleton, journals every package before writing, and undoes byte for byte. Preview is the default; CI gets an exit code.
UE 5.8, Win64. The code is AI generated. $14.99 on itch.