You can choose a set of templates saved in your sandbox space by using an appropriate sandbox prefix. For example, if you want to preview a version of සැකිල්ල:Test that you have saved as "පරිශීලක:Foo/වැලිපිල්ල/සැකිල්ල:Test", use "පරිශීලක:Foo/වැලිපිල්ල" as the prefix.