The Add Part 
command allows you to add a new tag part.
-
In the Create Master Tag Pattern section, select a tag part.
-
Click Add Part
.
-
Select an option to indicate where to add the new tag part.
-
Add Left - Adds the new tag part to the left of the selected tag part.
-
Add Right - Adds the new tag part to the right of the selected tag part.
-
-
Click Apply Changes
.
If you want to abandon your changes, click Reject Changes 
.