I ported my Text Editor to Haiku. It has features like Syntax Highlighting, Session Restore, Macros, Bookmarks, Plugins and more. You may want to try it out.
pkgman install python38 pip_python38 pyqt5_python38 qscintilla_python38 requests_python38 chardet_python38
pip3.8 install jdTranslationHelper EditorConfig
git clone https://gitlab.com/JakobDev/jdTextEdit.git
Just run python3.8 jdTextEdit.py to start it.
The Spell Checker does not work at the Moment because pyenchant is not working. Just ignore the error on startup.