Is there an "undo" shortcut in GTKInspector?

This debug tool is much improved from gtkparasite but Ctrl-Z doesn’t work as “undo” in the CSS editor. Is there another shortcut or was it removed entirely?

There has never been an “undo” key binding for GtkTextView—which is the widget used by the CSS editor. GTK does not currently have a generic undo functionality for its text widgets.