Spaces & notes.
A space is a directory. A note is a file. Everything else follows from that.
Spaces
Each space is a folder on your disk. Keep several — work, personal, a project — and switch between them from the sidebar or with ⌘O (CtrlO on Linux/Windows).
The sidebar tree
The sidebar shows your folders and notes as a real directory tree. Rename inline with F2, create a note with ⌘N or a folder with ⌘⇧N, and delete a note with ⌘⇧⌫.
Autosave & filenames
Writes are debounced as you type. A note's file is created on the first keystroke and named after its first heading — so the heading you write is the filename you get. ⌘S writes immediately.
External edits
The space folder is watched live (inotify on Linux, FSEvents on macOS, ReadDirectoryChanges on Windows). Edit, rename or delete files in Finder, another editor or a sync client and the change shows up instantly.
Session restore
abstract reopens your notes, window geometry and sidebar state exactly where you left them.