I was having this same problem. I’d also really like to see an official solution.
In the meantime, I modified the plugin myself to achieve what I wanted, and my solution for anyone else who is interested was this:
- Open intuitive-custom-post-order.php
- Remove ‘public’ => true from line 79
- Save and upload the new file.
- Open the plugin’s admin folder.
- Open settings.php
- Remove ‘public’ => true from line 32
- Save and upload the new file.
There are two issues to this method: Anytime the plugin updates, your changes will be overwritten, and removing the restriction against non-public things will cause Revisions and Menus to appear in your list of potential post types to change the order of. To me, this is worth it, but anyone who reads this will have to consider their own pros and cons for their particular situation.
Perhaps there could be some kind of custom flag that devs could set on their post types if they want it to be hooked by this plugin even if it is non-public? I have created post types that were non-public that I wouldn’t want to see custom ordered, and some that I have.