MoveComponentTo is declared at UKismetSystemLibrary::MoveComponentTo.

The action is updated in FLatentActionManager::ProcessLatentActions, in FLatentActionManager::TickLatentActionForObject and finally in the virtual function UpdateOperation (in FPendingLatentAction).

Callback is called here: CallbackTarget->ProcessEvent(...); (in TickLatentActionForObject)

MoveComponentTo

The action struct is FInterpolateComponentToAction