Long time no see - welcome back! How are things?
C2 is first and foremost based on HTML5, which means no direct reading/writing to disk. (Imagine if any website you visited could start reading and writing random files on disk!) Local Storage is a pretty recent addition that uses modern browser storage features. You can basically save text to disk, but the browser decides where to save it, so you don't specify any path or filename.
The easiest solution is: just store everything in the Dictionary object, but when you want to save it to disk, use Local Storage to save the Dictionary JSON data. To load it just read the same Local Storage key and load the resulting JSON string in to Dictionary.