I’ve recently asked for help with how best to handle radio (or other calendar-based) audio recordings. It would seem this is pretty poorly catered for in Plex at the moment.
The best method so far has been to use a music library with online metadata searching turned off, relying on that which is embedded in the file or part of the filename. I follow the Date-Based Television Shows format for file naming and all files are correctly tagged.
However, when in Folder view, there are no means to sort the list and the ‘Release Date’ column option is entirely missing.
In summary, please add column sorting in Folder view and the ‘Release Date’ column to make life easier for fans and archivers of radio and other calendar-based audio content.
I came here looking for this feature too. Then ended up using collections tags instead. Collections tags let you filter the default view by the collection tag and then you can use the sorting functionality that comes with that view. Works well for me.
Bill
Okay, I got something in the end. Not perfect and not automated, so this gets a weak 2 out of 5 for a solution, but it is a solution of sorts.
Collections were nowhere to be found because it seems that they don’t apply to Music libraries, where you get “Moods” instead. While clicking around for something more descriptive I hit upon the playlists function, where I was able to create a Smart Playlist for a radio programme, which in turn allowed me to sort by date added.
So, yes, I can get what I want so long as I’m prepared to go in there manually for every radio show. One down, one-hundred and fourteen more to go I suppose. 
Much better would be to just have the sort functionality on the folder view. 
