Issue in create file in mobile (ex:- test.txt)

Yes, that’s right, but that only applies if you target API 29 (Android 10):
targetSdkVersion = 29.

And this is not possible with Kodular at the moment, without adjusting the Manifest.

Scoped storage
To give users more control over their files and to limit file clutter, apps that target Android 10 (API level 29) and higher are given scoped access into external storage, or scoped storage, by default. Such apps have access only to the app-specific directory on external storage, as well as specific types of media that the app has created.