This doesn't work with customers being imported from multiple eCommerce websites, I think QBO should have multiple point of uniqueness to create customer files.
I have single customers shopping with me in multiple currencies from multiple eCommerce websites and the name and email are the same.
Thanks for the suggestion, surchling.
While we can't save lists having similar names, you can add a special character as suggested by our AllStars. Your feedback is a way on how we can improve our system more. I'll take note of this and for your to keep posted, you can visit our QuickBooks Blog, Any feature updates are posted there.
You'll want to use these links on how to handle your lists:
Let me know if you have other questions. Take care and have a great day!