you need to use Autodesk.Viewing.Private.GuiViewer3D to create Viewer default toolbars and ViewCube to appear, or in the context of Autodesk.Viewing.Viewer3D , create ViewCube and Toolbar

// ViewCube
const viewCubeUi = new Autodesk.Viewing.Private.ViewCubeUi( viewer );
viewer.viewCubeUi = viewCubeUi;

viewCubeUi.create();

// Toolbar
const toolbar = new Autodesk.Viewing.UI.ToolBar( 'my-awesome-toolbar' );
viewer.toolbar = toolbar;

// Button
var button1 = new Autodesk.Viewing.UI.Button( 'my-orbit-button' );
button1.onClick = function(e) {
    var state = button1.getState();
    if( state === Autodesk.Viewing.UI.Button.State.INACTIVE ) {
        viewer.setActiveNavigationTool( 'orbit' );
        button1.setState(Autodesk.Viewing.UI.Button.State.ACTIVE);
    } else if( state === Autodesk.Viewing.UI.Button.State.ACTIVE ) {
        viewer.setActiveNavigationTool();
        button1.setState( Autodesk.Viewing.UI.Button.State.INACTIVE );
    }
};
button1.addClass( 'my-orbit-button' );
button1.setToolTip( 'Orbit' );

// SubToolbar
const subToolbar = new Autodesk.Viewing.UI.ControlGroup( 'my-custom-view-toolbar' );
subToolbar.addControl( button1 );

toolbar.addControl( subToolbar );

only a few default tools are loaded through extensions, such as Autodesk.Section , Autodesk.FirstPerson , Autodesk.BimWalk , most of which are written in GuiViewer3D code, please go to viewer3d.js to find GuiViewer3D-sharpcreateUI () implementation ideas.

reference:

• create button: https://developer.autodesk.co.
• create a vertical toolbar: http://www.keanw.com/2016/05/.