Hey there! There isn't currently a way to delete multiple campaigns at a time, but I can definitely see how it would be a useful feature. I've switched this over to an idea conversation. If you have specific reasons for this, or any other idea for Emma, just reply and let us know!
Correction! And, I just learned about a new feature. You CAN delete multiple drafts of campaigns.
Select the campaigns using the check boxes to the left, then click the top-most drop down arrow (right underneath the create new mailing button) in the right column. Voila! You can delete all selected mailings.
On multiple deletions - can you make this more obvious: my account is getting overcrowded with every single save of a campaign. Also I have 10 times as many images as I need: multiples seem to proliferate. maybe have a question "DO you want to save this?" more frequently