If the list of the subject line is created for an email template which can be viewed or created from the path given below: "Punchh Platform >> Settings >> Email Template >> Select the template >> Select the Subject Line tab"
Now if any of the ones is default and you wish to select another then while configuring this Email Design or template in the campaign you will get the option of a drop-down menu to select the Subject line as shown below from where the particular configuration can be selected:
