Best I can tell, stationary was not meant to be edited, as you have discovered.  Use of a stationary starts a new message.  Saving that message as stationary processes as if you are saving a new stationary.  I also could not find a way to capture the content of the Details field from the Draft manager window.

Have you considered using templates?  They are more difficult to create but can be edited.  They also offer the benefit of prompting for information (values for string variables).

When one creates a Saved Message as Reusable Mail Stationery you get to give it a description on saving.  The To: address, followed by the email subject is offered as the default description.  You can change that to whatever you like, and often it is a long, hierarchy type name if you have hundreds of stationery messages.

If you open the message at a later time and edit the message, and then Save it, the system offers you the same original default and not the description (title) that was stored in the list when you first selected the message.  This means a laborious copying of the original description (title) from the list of messages.

 Is this a program bug or is there some way to configure the Message Editor.?

 Les