gtk:expander-new-with-mnemonic (label)

label -- a string with the text of the label with an underscore in front of the mnemonic character

The new gtk:expander widget.

Creates a new expander using label as the text of the label. If characters in label are preceded by an underscore, they are underlined. If you need a literal underscore character in a label, use two underscores '__'. The first underlined character represents a keyboard accelerator called a mnemonic. Pressing Alt and that key activates the button.