There are two additional fields for extra stuff for Projects and Tasks. They have a "Code" and a "Note". Either can be any text you desire.
We currently do not "collapse" the data into one line. Right now you could export all your data or you could filter on a specific Project code (each Time Entry would be a separate line). We may do some sort of collapse in the future, but I cannot make any promises to if and when it would get done. It it currently on our "wishlist" request from a couple users.