Context Menus for File Type Groups

I group various image file extensions together. I would like to include context menu entries, including opening particular applications, for the file type group, rather than going through individually. DOpus limits action types to "Run an Opus Function" and "MS-DOS Batch Function." How can I, for example, include an entry such as "Open with Paint.Net" for the group?

An Opus function can launch external programs. Simply set it up with the full path of your application as the command, followed by %1 to send the selected filename as an argument.

Trial and error led to the solution. Again, too simple!