Field help (TRKDEPCOD1) 

Help common to the functions: Shipments, Transports and Shipment pre-receipt.
SEEINFO In Shipment pre-receipt, this field is displayed and cannot be modified.

You can define a dependency link with another step, called parent step.
For an step to be selected as a parent step, it must have the following characteristics:

Once the step chosen, its description is displayed followed by the sequence number of the step in order to differentiate other possible identical steps.