How to get Filename of the config ini if I use custom UCLASS specifier 'config'?

Hi, I am creating custom project settings following How to add custom settings in Project Settings? - Programming & Scripting / C++ - Epic Developer Community Forums (unrealengine.com)

I want to access the value of those settings from reading ini configs so I followed How get Project Settings values? - Development / Programming & Scripting - Epic Developer Community Forums (unrealengine.com). However, I run into problem with the function

GConfig->GetString( const TCHAR* Section, const TCHAR* Key, FString& Value, const FString& Filename );

// sample usage, where GGameIni is a built-in variable that stores the path to Game.ini
FString AppVersion;
GConfig->GetString(
	TEXT("/Script/EngineSettings.GeneralProjectSettings"),
	TEXT("ProjectVersion"),
	AppVersion,
	GGameIni
);

When used with built-in project settings, it works fine, as the ‘Filename’ param can get auto determined(like GGameIni for ‘Config/DefaultGame.ini’). However, I dont know how to get the ‘Filename’ param if I declared a custom configName in UCLASS() specifier.

For example:

UCLASS(config = MySetting)
class TESTPLUGIN_API UTestPlugin_Settings : public UObject
{
	GENERATED_BODY()

public:
...
}

it stores configs in DefaultMySettings.ini, which cannot get from a built-in variable like GGameIni.

Does anyone know how to determine the Filename param for that function?

GetClass()->GetConfigName()
or
UTestPlugin_Settings::StaticConfigName()

When I use built-in name(e.g. ‘Game’), it can find that value. However, GConfig->GetString() returns false when I use a custom filename like ‘MySetting’. I tried GConfig->IsKnownConfigName(‘MySetting’), and it says no.