typedef TBaseDelegate_ThreeParams< void, const [TSharedRef](API\Runtime\Core\Templates\TSharedRef)< [SConcertSessionActivities](API\Plugins\ConcertSharedSlate\Session\Activity\SConcertSessionActivities) > &Owner, const [FConcertSessionActivity](API\Plugins\ConcertSyncCore\FConcertSessionActivity) &Activity, [TArray](API\Runtime\Core\Containers\TArray)< [FString](API\Runtime\Core\Containers\FString) > &ExistingSearchStrings > FPopulateSearchString