The PDF Viewer library allows you to open the thumbnail pane programmatically using the openThumbnailPane() method.
The following steps are used to open the thumbnail.
Step 1: Follow the steps provided in the link to create a simple PDF Viewer sample.
Step 2: Use the following code snippet to open thumbnail.
<button id="openThumbnail">Open Thumbnail Pane</button>document.getElementById('openThumbnail').addEventListener('click', () => {
// Open Thumbnail pane
viewer.thumbnailViewModule.openThumbnailPane();
});Find the sample, how to open the thumbnail pane programmatically