Forge Viewer PDF extension allow Document Browser to stay docked to side

I would like to keep the document browser docked to one side of the viewer with the thumbnails visible and no option to collapse the menu.

   export const initializePDF = async (url: string) => {
    const viewerDiv: any = document.getElementById("MyViewerDiv");
    const viewer = new Autodesk.Viewing.GuiViewer3D(viewerDiv);
    var options = {
        env: "Local",
        useADP: false,
    };
    Autodesk.Viewing.Initializer(options, () => {
        viewer.start();
        if (!url) console.log("error loading PDF");
        viewer.loadExtension("Autodesk.PDF").then(() => {
            viewer.loadModel(url, { page: 3 });
            viewer.loadExtension("Autodesk.Viewing.MarkupsCore");
            viewer.loadExtension("Autodesk.Viewing.MarkupsGui");
            viewer.loadExtension("Autodesk.DocumentBrowser");
        });
    });
};