Creating and managing templates
A template is a document that acts as a starting point for new documents. For example, the "1cm = 1m" template that comes with OmniGraffle has its units set up for drawing on a large scale. Other templates are set up with diagram styles which suit certain types of drawing. OmniGraffle comes with several templates, and you can create your own if you make the same kinds of documents often.
In the template chooser, you can choose a template for your new document. You can also create a new template, edit a template that belongs to you, or set a template as the default. Once you set a default template, OmniGraffle bypasses the template chooser and uses that template for any new documents you create. If you want a different template, you can still use the Template Chooser command in the File menu.
When you create an OmniGraffle template, everything about it is preserved, from the canvas size and grid layout, to layers, to visibility of extras, to the automatic layout settings. To create one, choose New Resource ▸ New Template from the File menu, then choose an existing template to begin from. Set up the document exactly the way you want it, then save it. The default save location is inside your own Application Support folder, where OmniGraffle looks for your templates. Once a template is saved in that location, it becomes available in the template chooser.