I deleted one of the four columns in my parking lot, and now I can't add it back. I'm permanently stuck with only three lists in the parking lot. Help?

So I had a redundant list in my parking lot and thought I would delete it and then add a new, less redundant one. However, now I'm stuck with only three columns and can't add back a 4th! There is no button to add another column. Please help! Three is way too limited for parking lot items.