PySimpleGUI is now closed-source
Take a look at the Source Distribution files: https://pypi.org/project/PySimpleGUI/#files
As far as I can see, it's still all just Python.
What's the best approach to avoid defining sqlite3 conn and cursor in many different functions?
I've always liked SQL, so I avoided ORMs for a long time... They are great for so many reasons! I definitely recommend you ORMs, specially the ones that also help you with migrations.