The WMS Path variable is located in the feature type editor and is a simple, optional, text field.

With this parameter you can tell the WMS how to format the GetCapabilities response. For example if you have a Feature/Coverage called Test and you write in the WMSPath field the string /today/tests/01/ then in the WMS GetCapabilites response you will have a layer tree like this:

|-today
  |---tests
      |---01
           |---Test