Current situation: When you insert a new template, suggested and required parameters are displayed (blank, of course) in the template dialog. When you edit an existing template, then only the parameters that were previously used/added to the template are displayed.
Preferred situation: If you are in the template dialog, then suggested and required parameters are displayed—no exceptions, new and old templates alike.
Always displaying all of the suggested and required parameters should make repairing or completing templates faster and easier.