Lightroom Classic not showing Collections

From your screen-clip:   {20230814_Sally Doughlas Book} is a FOLDER of your 19 files (as on your hard drive).

You also appear to have a Standard Collection of 29 images in a {SALL and ROBYN Book..} Collection.

Standard Collection of files are only useful when starting a new book (and I suggest ONLY when starting a NEW book!)

Now if you started a Book project by opening the Book module from any source of images (Folder or Standard Collection), you will not get a specific 'Book Collection' until you click on the Tab to [Create Saved Book] in the Book module.

Once a Saved Book Collection is created you must ALWAYS re-open to edit this particular book from the Saved Book Collection. (NOT a Folder of images, and NOT a Standard Collection of images.)