After installing Git and Homebrew, run:
brew install adwaita-icon-theme enchant gobject-introspection gsettings-desktop-schemas gtk+3 gtk-mac-integration gtksourceview4
python3 -m pip install pyenchant pygobject pyyaml
export LANG=en_US.UTF-8
export LC_ALL=en_US.UTF-8
git clone https://github.com/jendrikseipp/rednotebook
cd rednotebook
python3 -m pip install --user .
In Automator (run as Bash shell script):
export PATH=/usr/local/bin:$PATH
export LANG=en_US.UTF-8
export LC_ALL=en_US.UTF-8
/Users/me/path/to/rednotebook
(Thanks to Peter Green for documenting these steps at https://gist.github.com/pmgreen/a1bf2c7015cb2a70d73e5e66bb84885e based on https://jarrousse.org/installing-rednotebook-from-source-on-mac-os-x/)