emacs
Fe is a small and easy to use folding editor.
Fe allows to fold arbitrary text regions; it is not bound to syntactic
units. Unlike Origami, folds are not attributed with a trailing comment,
instead you can put folds before or after any text in the line, as you like.
Fe has no configuration or extension language and requires no setup. Its
user interface is emacs-like and it has menues for the very most important
functions to help beginners. Further there is a reference card. It offers:
* Regions and Emacs-like kill ring
* Incremental search
* Keyboard macros
* Editing binary files
* Multiple windows and views
* Compose function for Latin 1 characters
In case you can't stand the emacs interface and want ultimate flexibility,
fe can easily be modified, because it is structured as an editor library
with a user interface frontend, all written in C.