Thanks for the additional information, director9.

In Quickbooks Online, donors and customers/clients are the same. Currently, the option to change the customer label is only available in United States region.

I'll personally let our Product Development Team know about this feedback so they'll add this to other regions. They always take your suggestions into consideration when updating the product.

Also, it's is just the label when you create an invoice that indicates as Donor. However, they work as regular customers. 

Keep me posted if there's anything else that I can help you with.