To copy a variant you have to redirect to “Edit Variant” Page where the actions on variants are taken. Follow below path to copy an existing variant
Business Profile > Operations > Manage Inventory > Select Product > Edit Variant
You will be redirected to Edit variant screen
Select a variant you wish to duplicate and click on “Copy” button
The details of the selected variant will be opened in a pop-up. You can make the required changes in the pop-up
Once all details are filled, click on “Save” button and a new variant will be created from the details of the selected variant