"the thread I propose to add to, along with Mudcat in toto, has vanished from my desktop. When I get it back, the copy I have started has vanished, so I start again, and it vanishes again, and so ad infinitum ~~~ So what am I doing wrong"

Maeve said it before I got to it - and forget Internet Explorer - get and use Firefox - can have dozens of tabs open at once so you just pop from one to the other to do all this magic.

Actually, If I am in a hurry, i just post the plain html direct - it's not really all that hard to just copy that and paste it into a new blank tab in Firefox anyway...