Client-side encrypted plaintext editor that can persist/sync with GitHub Gists. All text is synchronized in an encrypted state. I had a similar use case to SDEES (Code on GitHub), but needed a zero-install, browser-based solution.
The editor is customized to my personal usage - CodeMirror in Vim mode for pure plaintext notetaking across multiple fixed-configuration machines (VDI, etc.). Often this includes confidential notes that I do not want to share with Google/Microsoft/GitHub, hence SJCL client-side encryption. Depending on your usage, you may want to inline everything in a single HTML file and/or add localStorage for offline/single-machine use, similar to Encrypted.