Barcodes can be switched ON and OFF from Settings screen > Barcodes in Katana.
Barcodes are included in the Advanced, Professional, and Enterprise plans (see more about subscription plans here). If you are using the Essentials plan, you will be asked to confirm the change to the higher plan (either a monthly or annual plan).
How to enable barcodes in Katana?
Note: If you switch barcodes OFF, the respective barcode fields will disappear but existing barcodes won't be deleted. New barcodes aren't generated when barcodes are switched OFF.