Look, you're not going to find something that satisfies you. The best you can do is a directory full of plain text and markdown files stored on a Dropbox or so

Look, you're not going to find something that satisfies you. The best you can do is a directory full of plain text and markdown files stored on a Dropbox or something. Then, on Linux use something like nvpy or one of the numerous text editors. Point it at the Dropbox dir. Write a bunch of helper shell scripts to automate tasks. On Mac, use something like nvAlt and point it at the Dropbox directory. Or go do the same thing I mentioned for Linux above. On Android, find some plain text notes app that lets you point it at a Dropbox folder. If you're into a cloud-based solution, take a look at Simplenote which has clients for all of the above.