Grave accent (`) - used to make this the default button (one for each dialog).
Caret (^) - the call-back function is called when the user clicks on the button.
Question mark (?) - a help string is supplied.
%bn is an alternative to %bt (Button) and %bb (Button). In particular %bn can be used to present split
buttons (with a down icon that is typically used for menus). It can also have the Microsoft "Notes" style of button with a
green arrow, title and notes. %bn takes the same modifiers as %bt and its width can be modified in the
same way via a leading integer value. Here are the options that can be used with %bn.
The caption for the button. "text=" can be omitted if this is the first option in a list.
The name of an icon resource to provide an icon (possibly with the "notes" style below).
Provides a green arrow (or your icon). The caption appears as a title with the text "Notes" below it.