To auto generate barcodes for variants, follow the below mentioned steps:
Please note that you cannot auto-generate a barcode when adding a product with variant. To autogenerate barcode for a variant, you need to add the product with variant first and then edit the variant."
Step 1: Click on the Products & Services.
Step 2: Select the Product with Variant.
Step 3: Select the Variant and Click on Edit.
Step 3: Click on Generate Barcode and click on Update >> barcode will be added to the Variant of the Product.