Go to Dashboard > Settings > General Price settings. 
Show return: Yes
Wait at drop off: Yes
Add new button
Time (hours): XX - this is the waiting time segment, you can create as many waiting time segments as you like.
Wait time flat charge: - input filed for additional charge for the waiting time. This fee will be added to Total if the customer selects this waiting time for Return trips.
Discount for Return (%): XX - this is a discount for the Return trip. You can leave this empty or 0. You can also use negative numbers eg. -10 which will actually increase the Return trip price by this %.
Now, when a customer selects Waiting time for Return trip in the booking form the calculation of Time (and price if selected) will be Base > Pick up > Drop off > Wait > Pick up > Base
If a future date is selected for Return trip then the normal calculation will be used: Base > Pick up > Drop off > Base > Drop off > Pick up > Base