@ Jo
re: we want to set up the directory so that people can manage their own listings but I don’t want them to log into the site itself, just the directory page
Sorry, this is not possible. WordPress has a built in proven, reliable and most importantly a secure user authentication system. A logon for just the directory is not a feature I will add to Connections when WordPress has one built in. My suggestion is to allow site login and have those users set as Subscribers. The only additional privilege a logged in Subscriber has is the ability to edit their WP user profile while being authenticated vs. a user which does not have have a login. You can block access to the admin for the logged in Subscriber. There are lots of plugins available to do this. Then you can use Form and link to give the Subscriber permission to edit their directory entry only on the site’s frontend.
Hope that answers your question thoroughly.
