Button to go to next or previous comment/highlight/annotation

The TAB and SHIFT-TAB keyboard keys will jump to the next or previous highlight. I would like to add two buttons to the toolbar to do this.

Opening the comment pane to click on comments takes up too much display space.

What function can be used to perform what TAB and SHIFT+TAB are doing?  I can't figure out how to jump to the next or previous highlight annotation in javascript, or how to get a button to emulate a TAB keypress.