Is it possible to put the Norton Utilities File Shredder icon in the Opus Directory toolbar?
You can add most programs to toolbars, as long as they can be run via the command line or a context menu handler.
In most cases, follow Editing the Toolbar and the Add a button that runs an external program part of it specifically, which will open the Launch Options dialog that you can use to test various ways of running the other program and passing file paths to it.
For things that can only be executed via context menu handlers, those are a little more complex, but the ContextMenu command docs have instructions on how to set those up.
Just a note. Opus has its own Secure Delete function.
"For confidential or sensitive documents, the secure delete function can be used to overwrite the file data before the file is deleted. The file data is overwritten using algorithms similar to those recommended by the US NSA and other security agencies. You can select the number of overwrite passes (from one to 31), although three passes is required as generally quite secure. Deleting a file in this way is much slower than normal, as every byte of the file must be overwritten one or more times, but it makes the original file data practically impossible to recover."
https://www.gpsoft.com.au/help/opus12/index.html#!Documents/Secure_Delete.htm