If you want to add some supplements to a transfer, that could be for example an “extra waiting hour”, “porterage” or some special tax, first you need to go to Admin > Transfers > Extras and define the supplement you want to add.
Here you can define:
For example, if we want to define a “Boat tax” because we have a transfer that needs to access a port, it would look like this.
Then, you need to add this extra to the transfer, to do this select Extras from the list of functions of the transfer you are editing. Here you can set the costs, the periods in which the extras will be available/will be applied, whether it can be on request.