Variable "entrySlug" does not exist Routing
If I'm not mistaken, I don't think setting up the route via the CP does the fancy advanced rule stuff described here. You'll therefore want to do that via the config/routes.php file with something like this:

'marketplace/&lt;authorSlug:[^\/]+&gt;/&lt;entrySlug:{slug}&gt;/edit' =&gt; ['template' =&gt; 'listings/_edit'],


Now authorSlug and entrySlug will be available for use in your listings/_edit.twig template...