Thanks for the suggestion, Ed.
The stock (racking) labels can be fully customised already. More information on this can be found in this post Additional Information on Product Labels or Customisable Labels - #10 by luke
Does this cover what you need, or do you need something else?
If you’re looking to change the word “Contains” to something else, you might want to check out the following information, Allergen labelling for food producers, and specifically this part:
For alcoholic drinks with no ingredients list, allergens must be indicated by the word ‘contains’ followed by the name of the allergen.
We don’t mind what you put on your labels, but I thought this might be helpful information as I know there has been discussion on this wording before 
If the label customisation tool that I’ve referred to above doesn’t do what you need, please can you let us know why and what you need? Cheers.