How do you write documentation for your Flutterflow apps?

I know Flutterflow has an icon to document certain parts of the program, but if you had to write a README.md for your Flutterflow app's documentation, how would you do it?

I think a Flutterflow app requires a special methodology for documentation, since Flutterflow is a visual app builder. I'm getting to the point where my app is getting big and I'd like to get some advice from those who have already had to document their Flutterflow app so they don't forget all the custom code they wrote and Flutterflow-specific actions they selected.