Defines tabIndex for sidebar element. This property will only influence the HTML if it's not 0. You can defined it during object creation: let sidebar = new w2sidebar({ name: 'sidebar', tabIndex: 5, nodes: [ { id: 'id-1', text: 'Level 1', hidden: true }, { id: 'id-2', text: 'Level 2', expanded: true, nodes: [ { id: 'id-2-1', text: 'Level 2.1' }, { id: 'id-2-2', text: 'Level 2.2' } ]}, { id: 'id-3', text: 'Level 3' } ] }); Or any time after the object has been created, if you re-render the object: w2ui.sidebar.tabIndex = 20 w2ui.sidebar.render()