Design Editing Mode (XML Schema Diagram Editor)
XML Schemas allow document designers to specify the allowed structure and content of an XML document and to check if an XML document is valid.
Oxygen XML Editor plugin provides a simple and expressive XML Schema diagram editor (Design mode) for editing XML Schemas. The schema diagram helps both the content authors who want to understand a schema and schema designers who develop complex schemas.
To switch to this mode, select Design at the bottom of the editing
area. 
Figure: XML Schema Diagram
To watch our video demonstration about the basic aspects of designing an XML Schema using the new Schema Editor, go to https://www.oxygenxml.com/demo/XML_Schema_Editing.html.