It would be useful to be able to hide the text input field of the inputbox so
just the button is shown.
Sometimes like on MediaWiki:Nogomatch you already have a default value that is
not needed to change so showing the text field is not nessary.
However it doesn't look very nice and it would be better to add a new option to
the inputbox extension.
So I suggest that a new parameter "hidden" is added so that "hidden=yes" hides
the text input field.