Just a heads up: PySimpleGUI 5 isn't open source any more [0], and the official GitHub repo was replaced with a stub [1]. From the blog post, it sounds like the people behind it will probably remove the FOSS version from PyPI soon.
It's possible the community will fork it with a version of PySimpleGUI 4 that's still kicking around, but I haven't seen one yet.
I'm the perfect target user for something like this -- long time "scientific" programmer, who is sometimes asked to create a useful little app for a limited audience. Nothing I write will ever see the light of day as a software product.
I use Tkinter. It was not hard to learn at all, and while it's not comprehensive, it gets enough stuff done. And it comes with the "vanilla" Python istall.
What I did with Tkinter, starting more than a decade ago, was to create my own little "wrapper" that simplified things even further. Each of my little functions or objects incorporates what I've learned about a widget and imposes a default -- ugly but functional -- layout. That way, I never have to look it up again.
It's possible the community will fork it with a version of PySimpleGUI 4 that's still kicking around, but I haven't seen one yet.
[0] https://news.ycombinator.com/item?id=39369353
[1] https://github.com/PySimpleGUI/PySimpleGUI