Is there a way to lay this out so it will fit better?

Please see attached screenshot..

If you look at the 'All listing categories' box on the left when adding a listing to my directory, I've begun to add breeds of dogs underneath the 'dog breeders' section. But I can foresee a problem. Adding over 100 breeds of dogs is going to make the content of this box ridiculously long and impractical to scroll through when wanting to add a listing for lets say a dog groomer.

Is there a way to lay this box out differently, or is there a way to make a separate directory just for dog breeders using this one installation of 'directory'?

I don't want my site to look messy because of one huge list of dog breeders on this page or the Link removed at members request page basically.

What are my options? Perhaps I could replace this box with a dropdown box which only displays the top levels until each top level is clicked on? Is this an option?