With mouse hover over custom button on ribbon, I get default screentip
(button label) and below a separator, my file name and "Press F1 for
more help".
I can leave without all of the above.
I can blank out the screentip by specifying a " " value for it (must
be at least 1 char long), but it still leaves a large empty space and
the file name with wrong 'Press F1' message.

Is it possible to hide it, and use it only when additional information
is really desired?