Having spent forever trying to figure out how to restore the Chrome Sidebar icon which for me disappeared in the update to version 124.0.6367.62, instead of the individual pinned items, let me document what I found as the steps to restore it. Info from a very long Google Chrome support thread:

 

     

  1. Open Google Chrome web browser and type "chrome://flags/" in the address bar and press Enter. It’ll open the advanced configuration page.
  2. Type "pinning" in the Search flags box.
  3. To re-enable the Side Panel button on Chrome toolbar, select "Disabled" from the drop-down box for the above mentioned option.
  4. Chrome will ask you to restart the browser. Click on “Relaunch” button to restart Google Chrome.

 

Background info from https://www.askvg.com/how-to-show-hide-side-panel-button-on-google-chrome-toolbar/