If I may attempt to help - trademarks that are artificial “Amazon store names” are most of what Amazon sees - a pathetic attempt by someone selling cheap plastic goods from China to differentiate it from the same exact product sold by dozens of other sellers who buy the same exact cheap plastic item from China.
Then there are true Brands, for example Nike and Nikon. They are operating as true brand names, in that they have a valid existence outside of Amazon, and they are a indicator of origin for a range of similar products.
Then there are smaller brands, which are often the name of a product. The name of the product is trademarked, but their is no “brand” hovering over it and the other products made by the same manufacturer. I am one of these - I have several trademarks, each unique to a product, and each is registered with Amazon’s “brand registry” as well as with the USPTO. I have no brand for everything I sell, as I make and sell unrelated items to widely divergent markets.
Each trademark has an owner listed at the USPTO, so one needs to create an Amazon brand registry account for each unique owner email address associated with a USPTO trademark, even if there is a different one for each trademark. The email listed at the USPTO will be used by Amazon to make contact and verify that the application for inclusion in the “brand registry” is legitimate.
Now, the relationship between the “brand owner” and the seller account is the tricky bit - the brand owner must delegate authority to the seller, so that the seller can file enforcement requests. One cannot file an enforcement request without a seller account, we were frustrated at this strange way of looking at the world, but there are several choices of the amount of “authority” you want to grant the seller entity from the brand owner, even if you are the same person.
So, ideally, the seller and the brand owner are two different entities, as Amazon cannot quite wrap its head around a small seller who makes a product sells it on Amazon themselves, and owns the trademark(s). Best to create a subsidiary entity for the Amazon sales anyway, so as to limit liability for product liability claims. Amazon sellers can get amazingly cheap product liability insurance, and this can keep your ISO CGL rates down, as Amazon is ummm… higher risk than other markets, just look at the “reviews” where people claim that stuff caught on fire when the item is a hunk of stainless steel.
But you can have more than one trademark on the “brand registry” managed by the same account if (and only if) you update the USPTO to make the email contact addresses the same for each of them before you apply to Amazon.
The brand registry is just incredible, as Amazon avoids all lability, and presumes to make itself equal to the courts. They have spawned a swamp of gibberish trademarks to be store names for crap no one really needs, available from dozens of wannabe middlemen, who are about to fold their tents when the expected tariffs make their crap double the current cost per unit.
Does your head hurt yet? Just remember, make a list of the email addresses listed at the USPTO, that seems to be the key to Amazon’s whole system.