Hi @flutterman,
Welcome to the community 
How do you want to access the generated CSV inside Flutterflow? (or how do you want the user of your app to be able to do with the csv data?)
I’m not familiar with Flutterflow myself but it looks like you can upload and save files on Supabase storage and access files from within Flutterflow. See their documentation here: Upload or Save File | FlutterFlow Documentation
The Supabase node in n8n doesn’t have the option to upload files so you’ll have to make custom API call using HTTP Request node instead. Here’s a related post that might help: Unable to upload file to Supabase storage bucket - #2 by n8n
For more help, it would help if you could post your workflow by sharing the workflow JSON here (between two ```) thanks!