I split my notes/todos into multiple files, but I wrote a small program which basically just creates a file with a randomized name in a flat directory and then opens it in my default editor.
I just want to be able to start typing right away without worrying where to put the note or what to title it or whatever. Like, I will put a title on it and include some keywords to help me find things again, but I can do that later when I don’t need to noting things down…