Thanks for the response. Where and when would I call this code? My xml file is loaded from a custom navigator. The SapphireEditorForXml is associated to the content type of my xml file so I never directly call the Editor.
This Java error typically means there is an issue with your plugin's manifest. Make sure that you included "org.eclipse.sapphire.modeling" and "org.eclipse.sapphire.ui" in your manifest's required bundles.