Your comments

This is already on the roadmap: http://roadmap.cintanotes.com/topic/3169-search-and-replace-inside-of-note-edit-dialog/
Also if you select some text in the editor and press F3/Shift+F3, you can navigate to next/previous instance of the same text.
Well, I agree that the comment covers it, but people usually vote for the headline and many of them don't read all the comments, so I thought it would be better to post this idea separately.

If many users express here their wish to merge these two ideas into one, I'd be happy to do it. But in this case we would remove the "individual note encryption" title and just leave the "Encrypted tags" title.
The difference:
here: mark a tag as "encrypted", after that all notes marked with this tag will require a password to view (probably once per user session);
there: select some notes and encrypt them, tags are not involved