Muffin Man Games

I know you can add the automatically created Mount and Pet bars.  But with over 100 mounts and over 150 pets, that is way more buttons than I really want or need.  I would like to be able to choose for the bar to just show my selected favorites.

There doesn't seem to be anyway of doing this on the default Mount bar.  So I was trying to build my own custom bar.  But there seems to be a glitch/issue with dragging and dropping the mounts into a custom button.  I can drag spells from my spell book, and items from my bag just fine, but I can't seem to be able to drag the mounts or pets from my spell book.

Is there a reason for this?  

I know enough of lua to be able to slightly read the code and would be willing to try my hand at working out a fix for this, if you could help me by sending me in the right direction.  Since I know you don't have much time on your own at the moment.

Thanks.