If I use the cart to order a pile of similar domains (X.com, X.nl, X.net) at the same time, I'd like to be able to label all the domains on that order, and/or add an individual label to a particular domain before checking out, so they stay neatly grouped once the order is complete...

Some domains aren't available right away, and so there's a good chance I'll just forget to come back later and them.

This would be especially handy if someone were using the API to fetch domains and generate configurations based on the labels applied to domains, for example.