Hey,
The plugin doesn’t have this feature right now. I think most users will find it confusing if there are multiple cropped versions of the same image in the gallery, they could accidentally make a crop out of crop for example.
The default WordPress image gallery also shows square images which makes it hard to pick the correct aspect ratio image. The only way this would be less confusing would be if the original images are not saved.
But this comes at the downside of having to track down the original image from your hard drive each time you want to make a different crop and you couldn’t make use of the re-crop functionality in the plugin.
I’m not really sure if there would be a way to create this functionality without making it really confusing to the user.