I understand how it should work, but I'm not getting the same result.
These are the things I do, steb by step:
1. I have attribute for size for example
2. It is assigned to the category
3. I create new product in that category
4. In Specifications I check the checkbox with size S
5. In Variants -> Add Variant I make new variant and check the checkbox for size M
When I open the product in the frontend I'm getting the appearance from the picture. No dropdown, the new variant is listed under the buttons.
I'm not sure if there is some setting that is required for that dropdown to show or I'm missing something else.