Field Config Cardinality doesn't work for widget : inline entity form - Complex

Yes you are correct there is no field widget defined for IEF. You can try to create the file in the src folder and extend the existing widget. It's probably a lot like the others.

With that said I will create a branch for the work. But one thing I wanted to do was configure tugboat so it's easier to develop for all. I will try and do that tomorrow so we can get a test environment setup.

I have created a patch for the same.