I concur: the note list is itself a side-panel that makes the editor/preview windows uncomfortably small in the desktop app (I’m running Linux). Another simple toggle – or including this sidebar in the “Toggle sidebar” feature-- would improve the Desktop app’s usability.
There is no need to see, permanently, a list of all notes in the current notebook when editing a note – I, at least, want to be able to focus on editing a note.