AppChooserButton.appendCustomItem

Appends a custom item to the list of applications that is shown in the popup; the item name must be unique per-widget. Clients can use the provided name as a detail for the #GtkAppChooserButton::custom-item-activated signal, to add a callback for the activation of a particular custom item in the list. See also [gtk.app_chooser_button.AppChooserButton.appendSeparator].