For the free ride fields there is the possibility to select a customer number for a free field with which a ride price is calculated.
The surcharge is now calculated as the unit price of the selected number. In this way, an additional charge for Baggage per item can be calculated.
Example
You want to charge a unit price per child seat in an order of 5 euros
First create the supplement of 5 euros
Go to my products / product settings / master data / surcharges
Make an allowance with a fixed value
Make the free ride field to child seat (see more about free ride fields)
Go to my products / product settings / master data / free ride fields
Select "Select number"
Choose the supplement