pyworkidprefix is the property which is used to populate the prefix of the work object.
pzPrepareSampleAssets is the activity which is setting this property in step 12.
This is a final rule and you can't make changes to this acitvity but you can reference this activity to create your own activity and call that activity when the work object is created to change the value of "pyWorkPrefix" property.
Please note that this property is present in Embed-Application-WorkMetaData class.
I am not sure if this is going to work or not but you can give it a try.