Is tmux+vim/nano the closest thing to the Notepad++ workflow (in recent versions of Notepad++ that automatically save session state)? I really miss that, it was convenient to just dump text I copied out of the browser to Notepad++ and just come back to it some time later, but I'm not sure what the closest thing in Linux is.
On command line, vim/tmux is probably the closest you'll come. For desktop apps, Sublime Text will restore anything opened with any changes you made (saved or no). There is a feature request here to add this to Atom, and the save-session plugin is available until such a time as it's rolled into the core (which may be never, admittedly).
Edit: There is also a plugin for gedit available here