This reply is very late so, hopefully, you have solved this by now. If not:
Right click on the iCloud folder in your Outlook on your PC and you should see "IMAP Folders"
Click on that and see a box with tabs labeled "All" and "Subscribed"
Click on "All" then click on "Query"
Your computer will search for all available folders and you can highlight any of them and click on "Subscribe" or "Unsubscribe" to be able to see them (or not) in the Outlook on your PC.
Hope this helps.