Indicates if flat button should be displayed. Flat button is a small button in the top right corner when sidebar is not in the flat mode and on top when it is. If user clicks on the flat button onFlat event will be generated. You can define it during object creation: let sidebar = new w2sidebar({ name: 'sidebar', flatButton: true, nodes: [ { id: 'id-1', text: 'Level 1' }, { id: 'id-2', text: 'Level 2' }, { id: 'id-3', text: 'Level 3' } ] }); or during run-time: w2ui.sidebar.flatButton = true; w2ui.sidebar.refresh();