Most capabilities structs seems to be not a derived struct from an interface or base struct.
Check UE_DECLARE_MOVIESCENE_PLAYBACK_CAPABILITY_API macro usages for examples of declared types.
Types
IPlaybackCapability
Interface for playback capabilities that want to be notified of various operations.
FSequenceDirectorPlaybackCapability
Playback capability for sequences that have a director blueprint.
FMovieSceneEvaluationState
Provides runtime evaluation functions with the ability to look up state from the main game environment.