To keep some notes organized and easily accessible, I currently use Notable, a Markdown note editor. It leverage Monaco under the hood, and is capable of using tags as an hybrid tag/directory structure.
It's not capable to synchronize itself but the working directory can easily be managed in a git repository so you can have your notes everywhere you can clone a repo.
I originally ditched that tool because it kept overwriting my notes, but that nasty bug is fixed, and feel pretty rock solid now !
Cool bonus, all major systems are compatible and have their packages/installers available in the release page.