@ Rebecca
RE: I want my members to be able to login to add or edit their own entry without creating a WordPress account. Would that be possible?
I think the answer here depends on what is trying to be accomplished…
If you want members to be able to login and be able to add and edit their own entry in the directory. That user must be logged in as a WP User. To make edits the user has to be authenticated somehow and the WP user authenticate is a proven secure method. Adding a separate way to login would be against best security practices. The WP User at a Subscriber role does not have much more privileges that a not logged in user. They can maintain the email and password and that is about it. You would configure Link but not enable the “Submit Entry” link.
Now, if you want any random user to be able to submit, moderated, submissions to the directory. Yes, this can be done. You only need to use Form and configure it to display the “Submit Entry” link above the directory.
Ok, now, if you want both of the above, you would configure both Form and Link. This would allow site visitors to submit, moderated, entries. Allow your logged in WP Users to add and maintain their own entry. The important bit here is they would only be able to edit their entry, not any additional entries they may add (I think, it’s been quite a while since I tested a config like this). Your users may find that a little confusing.
I think and hope I have answered your questions. Let me know.
Hope this helps!