It's faster to debug in the Editor, so this made my life simple:

#if UNITY_EDITOR
rootFolder = Application.dataPath+"/RootFolder/";
#elif UNITY_ANDROID || UNITY_IOS
rootFolder = Application.persistentDataPath;
#endif

It's faster to debug in the Editor, so this made my life simple:

#if UNITY_EDITOR
rootFolder = Application.dataPath+"/RootFolder/";
#elif UNITY_ANDROID || UNITY_IOS
rootFolder = Application.persistentDataPath;
#endif

And from the rootFolder, you build your file system structure (cross-plateform).