As normally, products with several options such as size, color .etc will be created as configurable products in Magento, which contains simple products for each option. By default, these simple products will contain separated SKU. In reality, Kootoro manages some products with several sizes, colors but wants to keep the products in unique SKUs. This is the instruction to deal with the situation.
In summary, there are two main steps:
On the admin sidebar, go to Catalog > Product.
Go to Products page, find the product to edit, then click Edit under Action column.
On the product detail page, expand the Customizable Options section.
Drop-down
Radio buttons
Checkbox
After finish, click Save button on the top right to save the changes.
The product type does not change.