As the post (and a number of others like it) indicates, you can’t have duplicate text values in a list. A potential solution for you is to have a Product data type and save each product as a thing in that data type. Because each thing in the data type is unique, it won’t matter if two products have the same name.
Just some friendly advice… if you don’t know how to create a thing in a data type (which is about as basic as it gets), you are really going to struggle on your Bubble journey. You should definitely consider taking some time to work through Bubble’s tutorials… they are great when it comes to learning and understanding the basics.
The above being said, I created a quick example for you…
Create a Product data type with a name field.
Delete the Product Name field you are showing in your fourth post in this thread, create a new Product field with a Field type of Product (i.e., the Product data type you created just above) in that data type, and make it a list.
When the button you are showing in your first post in this thread is clicked, use the Create a new thing workflow action to create a thing in the Product data type.