This feature is meant to disable input in a dialog to prevent accidental input, in case the user happens to be typing or clicking at the time that the dialog is displayed. It is meant to work in a consistent way in all dialogs. So a 'bN' option is not something I would want to add.
However, the X button should also be temporarily disabled in the same way as other dialog buttons, as it could be accidentally clicked when a dialog is first displayed. I will make this change for the next version.
