When the "Contents" menu is opened as a sidebar, dragging the thumbnail of a page results in the app suggesting to open a copy of the current notebook in a new window. This issue is only present when the Contents menu is opened as a sidebar---the dragging behaviour is completely fine when the Contents menu is opened as a window. This has been quite a nuisance to me every time I am trying to reorder the pages in my notebook by dragging page thumbnails in the Contents menu when opened as a sidebar, since the app almost always tries to open a new window in these cases (see attached screen recording of me trying to reorder my pages). My suggestion is to make the behaviour of the Contents menu as a sidebar consistent with its behaviour as a window by stopping the app from suggesting to open a notebook in a new window when dragging page thumbnails. The option to "Open in New Window" is already present in the dropdown menu from a page's thumbnail anyway (see image), making this feature redundant.