Happy to help. 
It’s probably worth pointing out that the AnKing Step deck is primarily curated with the Step exams in mind, so it may have varying utility if you’re studying for something other than those exams, just FWIW
That doesn’t mean, obviously, though that it won’t be useful in various ways but the overlap might be variable depending on the specific constraints of what it is that you’re preparing for
I’m not sure which exam, or goal, you’re preparing for which might make it a bit tougher to offer recommendations. But, the short version is that there isn’t an easy first-order way in the AnKing deck to study only by systems, as the deck hasn’t traditionally been organized that way
It is the case, of course, that people do learn by systems, though most often they are doing so alongside a third-party resource (BoardsAndBeyond, FirstAid, etc.) and so tags tend to follow along by those resources instead. Some of this is due to how folks typically approach the material, and some of it is also due, by necessity, to thetypical workflow in how the deck was tagged
If you are wanting to study by system, let’s say cardio (as a random example), your best bet might be to make a subdeck for the cardiology-related cards from a couple or a few resources and thus isolate the majority of a system’s card content in a given subdeck. It’s not common for many users to organize their collection based on subdeck for a number of reasons, and this might be the likeliest solution to your problem, given the organizational constraints of the deck
This tutorial is a very basic example of how you might go about creating a subdeck and moving topic-specific cards into that subdeck: How to Create Subdecks
Let me know if that helps cover some of what you’re aiming for, if there’s anything else on which I can help offer tips or advice, and anything else I might be of help with. 