If the travelers you just dropped off want to book Welcome in another destination, you can book it via your Driver's App!
Just follow the same process as you would when booking a return transfer (found here) and at "Step 4" just select the destination city that the traveler requested!
The transfer request will not be sent to you but you will still get the extra points that count in your total score that defines your leaderboard position.
Note that while trying to book the transfer for the travelers, if you cannot find the city in the drop-down menu, it means that Welcome does not operate yet there.