The toolbar item click event is an event of the editor. You should add an event handler to the smart editor.
It is expected that you receive an empty array because when the component mounts the smart editor has not been initialized yet.

See the console when you click a toolbar item here: https://codepen.io/svetoslavb04/pen/BaPYmKZ

If you have any additional questions, do not hesitate to contact us!

Best Regards,
Svetoslav Borislavov

Smart UI Team