I love the simplicity of this idea, however there also are some potential problems. I think the concept of the all-purpose remarks field would be more difficult to understand for the new users. Also it will make difficult introduction of additional filters: there will be no more solid information on the URL the note comes from. So for example it won't be easy to build the list of domains (like in browser history). In this way this simplification will be hindering further useful features. What do you think?

I think this is what is meant here: tags which are present in the current view should be displayed differently from tags which are not visible at the moment due to the search filter (just because no notes with these tags happen to be in the filtered list).

Sorry for the delay.
No I envision it a bit differently: you double-click on a tag, not on notes. After that only related tags remain in the list. To go back to the full list, you will have to deselect the initial tag you have double-clicked on, or explicitly switch to "All".

About the hotkey: probably not since Tag sidebar is by design mouse-oriented. Maybe the same behavior should be provided for tag autocomplete, which is keyboard tag interface.

Sorry for the late reply.
Thanks for the ideas. I think it would be better to post them separately: I consider note numbering, note pagination, and note number filter to be quite different concepts. Maybe then there's be more upvotes as well.

Returning to this issue: no, the keys will be used in the notes list as well. About using Ctrl+Del for deleting notes - I don't think that's particularly user friendly. We need to think of something else) 

Please tell which kind of encryption you'd like to have:
1) Encrypt whole notebook file (when CN is running, the file is decrypted)
2) Encrypted tags (decrypt on command, with timeout)
3) Encrypted individual notes (decrypt on access, encrypt on close)

Thanks! 

I think that note grouping can be really useful, but I'm not sure about grouping by tags. Tags are non-linear, that means that one note can appear in this list more than once. Is that what you intended?