sorry itrotta, looks like it simply isn't possible. I have had to go through the process of creating one csv file per adgroup. bit of a silly thing to be missing imho, but such is the headache of adcenter.
Hi all, You could try our Quick Launch program...it's a service where a media specialist can help you get your campaigns migrated over to adCenter. You can fill out this form (https://advertising.msn.com/microsoft-adcenter/quicklaunch/signup), and you should be contacted about 48 hours after they receive it.