You can add folders and snippets to Visual Studio over Tools > Code Snippets Manager
I have created snippets with your extension and placed them in a custom folder, which i added to Visual Studio with Code Snippets Manager.
Your SnippetExplorer displayed the snippets just fine after a search, in the Visual Studio session i created them, but i couldn't open them. Got an error message.
However after a restart of Visual Studio, your SnippetExplorer doesn't find my snippets in the custom folder at all.
The custom folders are stored in the registry at this location:
There are multiple entries for each coding language, each entry has a path folder containing a key with the name of the language and the value containing a string with all paths including custom paths seperated by ';'
Key: Microsoft Visual CSharp