addling a stop on the 660

I was going to a place in the city when i realized that i wanted to park in a garage. so i opened the parking map and clicked on the nearest one. I was assuming it would ask me if i wanted to add it to my trip, but instead it stopped my original destination and routed me to the garage. Is there some settings that im missing to add places along the way on a trip without losing your final stop? Thanks

cosmo4u