Thanks jford, I think it's starting to penetrate my hard head that what I was trying to do in the graphic events panel with view/edit set to "velocity" simply can't be done, and that the lines/curves disappear upon releasing the mouse button precisely because they don't function in that setting.
I've been making nice fades with a "control 7 Main Volume MSB" setting for view/edit, so I'm happy to have a working solution and I'm happy to have discarded a muddleheaded idea (with help from you all).
Clinton.