We've actually been in touch with Alejandro over at Reviews for Joomla about some things he (and his customers) would like. Create a new listing is definitely one. Unfortunately, I'm not sure if you can do what you're looking for with the Custom Actions ability since you'd need to hook into their system a little more tightly than that may let you. Alejandro recommended creating a jReviews specific plugin which has triggers for New Listing (and other things), and that's something we're looking into.
The good news is that our method we're planning *should* also work with moderated submissions.
The bad news is that I don't have an exact timeline on when that would be available, but it will definitely be either later this month or in January.
We're excited to add a lot more Joomla-specific actions and really appreciate the feedback on what you're looking for. Hopefully, you can wait a little longer!
Thanks,
Alex
Action for submitting JReviews listing
