In the EMD, when you proof launch, you can send to a pre-built proof list OR manually enter email addresses you want to send a proof launch.
Manually entering email addressed is limited to about 256 characters, which is maybe 6-8 email addresses.
We tend to have much more extensive lists which require sending a proof launch multiple times to cover everyone that needs to receive a proof launch.
These lists vary on most emails we proof out, which is why we don't have pre-built lists for this purpose.
Even doubling the current character count of 256 to 512 would be a vast improvement and make proof much easier and faster.
Obviously if we can get the character count up to 1024+, that would be most helpful and allow us to never have to send more than one proof launch to cover a list of people.