To include the newly published catalog(s)/handbook(s) in the drop down catalog menu available on all published catalog pages, check the "Show in catalog list" checkbox on the catalog cover item and republish.
The first image below is an example of a drop down menu of catalogs on a clients live catalog page:
The checkbox to include the catalog in this drop down menu is located on the catalog cover item, in the "Catalog List" section:
To include the selected catalog in the catalog drop down menu, check the box as indicated, save this update and publish the cover:
Please be sure to uncheck the "Include Subitems/Related items" checkboxes on the publishing wizard to publish just the selected catalog cover item when making this change: