No, sadly that does not help. This post is not of an issue of no thumbnails appearing. Thumbnails for any other type of file format work perfectly fine on my install. I know thumbnails for .pdn files will work if I "install" Paint.NET but I wish to use the portable version instead, therefore I did not install it and therefore do not have thumbnail functionality for .pdn files, hence why I made my own ShellExtension to do this instead (so I dont have to install paint.net).
And still... my original question was... which subforum do I post about such ShellExtension I made?