I try to keep my notebooks organized. I find this to be a challenge since all of the notebooks are in one big “pile” (as opposed to being “inside” folders as in a hierarchical file system). One way I do this is by trying to make sure every notebook is assigned to (at least one) relevant collection.
It would be great if the Notebooks page had a Filter for In collection(s)/Not in collection(s). This would make it very easy to find “orphaned” notebooks.