Emacs has multiple built-in libraries for folding code, as is the case for most things Emacs. The default interface it exposes for folding functions is unwieldy and cumbersome, as is the case for most things Emacs. There is some overlap between Hideshow-mode and Outline-minor-mode. The latter is mainly for folding and navigating nested Org-like headings, but can be extended with the Foldout library. (Also included in Emacs!) The former works well to hide nested blocks of code.
