Thank you Jerome,
Jerome wrote: 2 - If you take a look at that page in the demo website :
demo.hikashop.com/index.php/en/hikashop/product-page/with-form
You will see a product page with a form ; you can imagine that in that form, you will find a dropdown list where the user will be able to select any published vendor of the website.
So if I understand correctly first I need to create characteristics, then based on these characteristics create a product variant which will force the user to select a vendor when they add a product to the cart?
In my case the users don't know which vendor they need to select. I need to select the vendor for them somehow based on the access level, but don't really know how I can do this?