This might be out of scope, but I think it would be useful to have a notes text field that could be entered next to each domain in the whitelist & blacklist.
You could enter any information that proves useful to you to remember when or why a domain was added. For example, you could add the date it was added, a url or service it's intended to fix or block, or the user or device that it was added for.
I find this very useful, too!
Sometimes I do some whitelisting and later don't know what was the reason.
This could be written in a short comment besides.
I'd love to see it implemented!