Unfortunately changing products from single variant to multi-variant or vice versa on Trade Me is not possible.
You cannot add variations/options if the product is listed already
You cannot rename variations/options if the product is listed already
In any of the cases above, the existing listing needs to be terminated, deleted from our database and the product re-listed as a new product.
You will need to submit a ticket to have the item deleted, when doing so please include the SKU and the exact Product Name.