Short answer: no. We don't support adding variants to products that Single creates for you. Editing a Single-created product this way typically breaks delivery and reporting for the release.
If you want a single product page where fans choose a format (for example Vinyl, CD, and Digital), don't modify the Single-created product. Set it up on a product you own in Shopify instead:
Add a Digital format to an existing product — see Adding a "Digital" variant to an existing Product in Shopify.
Sell the album on its own page — see Selling a Digital Release as a standalone product in Shopify.