This would be a great feature for me! One use case would be when bookmarking a software library, there are multiple links you might come across: the homepage, the documentation page, the source repo, some 3rd party tutorials, blog posts, et al.
I would also use this feature. Many times I'm clipping a URL and saturating my notebooks with a new note just for a link.
Ex. Links for tutorials on a specific programming language or app, etc. So a note is my topic and would just append the link to the not instead of creating a new note. A drop-down for selecting from all notes is not practical - maybe show a new dropdown after the notebook is selected.
I guess we would need to have another radio option:
Type: New Note New Todo Append to Existing Note/Todo