Prevent Ctrl-Alt-Del on AppStream from `FN Keys` toolbar

Can you enable the FN Keys toolbar on AppStream 2.0 (in an embedded webpage using appstream_embedd.js) but still prevent the end user from using these soft function keys to press Ctrl-Alt-Del, getting access to the Task Manager?

(Task Manager is not listed in our Application Catalog. From the Task Manager any applications can be started without consideration of the Application Catalog, including powershell, Explorer etc.)