When you right-click on the name of a notebook to move it into another notebook, the list of notebooks under “Select...” shows all the notebooks in the trash along with all the others, without distinction. This can lead to accidentally sending a notebook to the trash.
To be honest, this can be considered as a bug rather than a feature request. Also, if you right click and choose restore note for an individual note within a notebook which is in the trash, the note will have no notebook and only show in the all note notebook