In the google apps script editor for google sheets, I can add a library created by others if I know the project key e.g. MKvHYYdYA4G5JJHj7hxIcoh8V4oX7X1M_ (a library for acc
Just copy and paste in the URL:
https://script.google.com/d/(THE_SCRIPT_ID)/edit?usp=drive_web
Eg. https://script.google.com/d/MKvHYYdYA4G5JJHj7hxIcoh8V4oX7X1M_/edit?usp=drive_web