Hi @mrblond,
Sorry for the confusion. In the original/old version of the plugin, a separate “Folders” page was generated for each post type that had folders enabled (rather than being integrated directly onto the built-in WordPress list view pages like it is now). The checkbox you’re referring to is on those pages. If you want, you can enable those pages by going to Settings > Wicked Folders and checking the box next to “Enable legacy folder pages”.
In the current version of the plugin (which has the folders integrated into the admin list views of things like pages and posts), you can view unassigned items by going to the Dynamic Folders > Unassigned Items folder.
I hope this helps! Please let me know if you still have questions.
I see. Thanks for the response.