Leo Editor

Leo (Leonine Editor with Outlines) is an open-source text editor/outliner that features clones (virtual copies of outline nodes) as a central tool of organization, navigation, customization and scripting. == Languages == Leo can manipulate text or code in any human or computer programming language (e.g., Python, C, C++, Java), as Leo is a language-independent or "adaptable LPE" (literate programming environment).