Hi,
Yes, that's an option of both the Essential and the Business editions. However, I can see that you have the Essential edition in your account on our website. Are you not using it ?
It means that if you don't finish a checkout for a cart, let's call it AAA, and you login while having a cart BBB as a guest, you'll end up with 2 carts linked to your account. And then, when you go through the checkout for that cart BBB, BBB will be deleted once the order is created for it, and the system will then display you AAA as your current cart.