Templates
 

I have been experimenting with making templates (canvas sizes and units).

How can I delete those no longer required, and rename others?

User-created templates are stored in ~/Library/Application Support/OmniGraffle/Templates, and you can simply delete or rename the files. Use the Finder's Go->Go to Folder... command, and enter that pathname to go to the folder in a single step.

You can also create folders in that folder to organize your templates.

Thanks for advice, I have managed that, but still have a problem.
I have a 'rogue' template that I cannot get rid of. It shows when I look in the Templates using OmniGraffle, but not shown when using Finder. It appears that it is a backup or autosaved copy of another template. (Don't understand the inconsistency between the packages looking in the same folder.)

Interesting. I'm not sure what might be going on there. Have you quit and reopened OmniGraffle? If you still have the original template file open in OmniGraffle, you can cmd-click on the window title and get a list of the folders showing where it is. You might also see if a freshly downloaded copy of OmniGraffle still has the rogue template—maybe you somehow managed to save the rogue template into the application bundle next to the built-in templates?

I apologise that I can't explain how, but I have managed to get rid of the 'rogue' template, so I now have the different variations I expect to use. Thanks.