I tried this in Pine 4.33 on various Unix flavors. See if anyone else can
(C)ompose a new message. ^O(Postpone), then (M)ain (S)etup (C)onfig, and
add something to customized-hdrs.
Now, (C)ompose, and resume the postponed message. (^R)ich Headers. The new
header that you just added doesn't appear in the headers list. If you
compose a new message however, the new header does appear in Rich headers.
I came across it when I posted a message, and wanted to set the followups,
but realized that I hadn't added that header to my list.
I see no reason why this should be the way it is. If it's not a bug, then
in my opinion, it is a misfeature. Comments?