When a product has variation options you will see one row for the product by default, and it will contain a blue "expand" arrow to the left of the product:

Clicking the blue arrow will expand that specific product to show all the available variation options and their stock levels:

If you have a lot of variation type listings, you can make them all expand at once, simply by clicking the white "expand" arrow in the top left corner of the Products table, and then you will be able to load every individual variation SKU to more easily view and edit available stock and other product/listing management functionality: