The plugin does not have a wild card feature. It is designed for simple redirects, so it was intentionally left out.
This is one of the cases where you would want to use something like .htaccess. A simple bit of code should work fine.
The .htaccess file is in the root folder of your site (where the wp-config .php file is located). If you do not know how to edit your .htaccess file, search on Google, use a plugin like http://wordpress.org/plugins/wp-htaccess-control/screenshots/ or read something like this tutorial http://www.shoutmeloud.com/how-to-edit-your-wordpress-htaccess-file.html.
I also want to point out that editing the htaccess file is at your own risk. It is the easiest way to achieve what you want to do, but doing it wrong can make your site not load - so be careful!
Add this to the .htaccess file BEFORE any WordPress stuff you see like,
# BEGIN WordPress:
Redirect 301 /slug.html /slug/
Change the word
slug to the file name and the slug you will need changed. You can change
301 to 302 if you only want to return a temporary redirect response. That should redirect and keep the Query String data attached.