This feature has been added now since version 1.3.
Now you can click the media buttons on top of the editor, browse to Media Library and select a previously uploaded image to set as your featured image.
Unfortunately, due to the lack of hooks present for this mechanism the page will reload once you do this, but that should not be an issue.
I hope that this resolves your problem 🙂
Thanks for using my plugin, and be sure to rate it as you see fit.
@zetoun17: Do you still think this plugin is only worthy of two stars? I’m just trying to make sure the plugin gets honest reviews and since all your problems have been solved then maybe you think it’s better overall now?