I've taken over maintenance of a multi-site Magento store & need to create a new layout to be used on certain products. I know I can select a custom layout in the design tab of the Product Information page in the back-end. What I don't quite understand is how I make a new layout to appear in the drop-down list here. I've looked at tutorials but nothing really seems to cover this. Am I right in thinking that I need to create something like newlayout.phtml in the theme's layout folder?
Any help, tips, advice, or tutorials would be gratefully received.