Thanks Nicolas for your answer. I understand your point of view but that's a pain for lot of cases.
Imagine that Product A has got color as variants. It's obvious that adding a "No" option have no sense, and this is a very commone usage. Example a T-shirt (red, green, blue) that I can add as option to a pair of trousers, but when I buy that pair of trousers I don't have to buy EVEN the T-shirt, so I could choose a "No" option. But when I by the T-shirt it has no sense that I see the "No" value in the Color variants.
Also I saw in your demo site that to avoid this issue you created 2 different products for the same good. Example you have 2 webcam created for the same product. The first one you sell without the "Without" ("No" in my case) option and the other one with the option "Without".
You see that this is a nice trick to let it work correctly but it not the right way it should work also if you have really lot of product to manege.
The best way should be that when Product A has got 3 variants (color for example, and it's obvious that I must choose one of them and a "No" value have no sense) if I use it as option for Product B, HikaShop should display me a parameter (in backend option's manager) to add a "No" value.
Would you consider this important feature in next releases?
Thanks in advice.