I couldn't find any information regarding this. Thanks!
The button appears automatically at the top when you have a long description. But your games have shorter text, so the one at the bottom is already visible without scrolling.
I want to add the ability to explicitly control whether or not it shows in the next update to the theme editor, hoping to have it out soon.
Thanks, yes I think having the buy/demo buttons on top would be a good idea. Could also just be a HTML tag/special code in the editor so people can place them where they want :)