FindBlueprintsWithAssetRegistry.cpp

FAssetRegistryModule& AssetRegistryModule = FModuleManager::LoadModuleChecked<FAssetRegistryModule>(TEXT("AssetRegistry"));
IAssetRegistry& AssetRegistry = AssetRegistryModule.Get();

// Optional
TArray<FString> ContentPaths;
ContentPaths.Add(TEXT("/Game/My/Folder"));
AssetRegistry.ScanPathsSynchronous(ContentPaths);
// End Optional

TSet<FName> DerivedNames;
{
    TArray<FName> BaseNames;
    BaseNames.Add(UMyBaseClass::StaticClass()->GetFName());

    TSet<FName> Excluded;
    AssetRegistry.GetDerivedClassNames(BaseNames, Excluded, DerivedNames);
}

FARFilter Filter;
Filter.PackagePaths.Add(TEXT("/Game/My/Folder")); // optional
Filter.ClassPaths.Add(FTopLevelAssetPath(UBlueprint::StaticClass()));
Filter.bRecursiveClasses = true;
Filter.bRecursivePaths = true;

TArray<FAssetData> AssetList;
AssetRegistry.GetAssets(Filter, AssetList);

TArray<TSoftClassPtr<UMyBaseClass>> FoundClasses;
for (const FAssetData& Asset : AssetList)
{
    auto GeneratedClassPath = Asset.TagsAndValues.FindTag(TEXT("GeneratedClass"));
    if (GeneratedClassPath.IsSet())
    {
        const FString ClassObjectPath = FPackageName::ExportTextPathToObjectPath(GeneratedClassPath.GetValue());
        const FString ClassName = FPackageName::ObjectPathToObjectName(ClassObjectPath);

        if (!DerivedNames.Contains(*ClassName))
        {
            continue;
        }

        FoundClasses.Add(TSoftClassPtr<UMyBaseClass>(FSoftObjectPath(ClassObjectPath)));
    }
}

// FoundClasses now has a list of *soft* class pointers.