The Modelling logic central to MDrivenDesigner and MDriven for VisualStudio has a Plugin infrastructure.

The infrastructure is described in further detail here Modlr plugin

It loads plugins located in the path decided by this code:

private const string RegKeyName = @"Software\CapableObjects\Modlr";
public static void LoadPlugIns()
{
  string path = Environment.GetFolderPath(Environment.SpecialFolder.CommonApplicationData);
  path += @"\CapableObjects\Plugins";
  Microsoft.Win32.RegistryKey key = Microsoft.Win32.Registry.CurrentUser.OpenSubKey(RegKeyName);
  if (key != null)
  {
    path = key.GetValue("PluginPath",path) as string;
  }
  System.IO.Directory.CreateDirectory(path);
  LoadPlugInAssemblies(path);
}

As the code shows you can override that path by createing a registry value: