So you thought you were all done after finally figuring out your Enneagram type + wing + instincual variant stacking? Not so fast. Now they’ve added something called “tri-fix” to the fine tuning of your main type. I shouldn’t say it that way, like someone just came up with it yesterday. But it is fairly recent; I first learned about it less than a year ago.
In a nutshell you decide your type (“window”) in each of the 3 triads: feeling, thinking, instinctive. For instance, if you’re a 6, you already know what your type is in the thinking triad (5,6,7). So you start out with the triad of your main type. From there you go on to the following one: in this example, the instinctive triad (8,9,1) and decide which of those. Say you identify most with type 8. On to the feeling triad, 2,3,4. Say it's 3. Congratulations, you’re a 6-8-3, which should make you a noticeably different kind of 6 than, say, a 6-9-4.
But wait, there’s more. Now you have to figure out your wings for each of the main types in your tri. What you end up with is your advanced subtype being something like sx/soc 6w5, 8w7, 3w2. If you’re interested you should read more about this on an Enneagram site. But I think I pretty much gave you the gist of it. If you already have a good feel for all the types, you can work out your tri-fix on your own. Otherwise you have to pay for an online test or else take a test like the RHETI indicator in the Riso Hudson book and go by your highest scores in each triad. But I think you need to know and have a good feel for the essence of each of the types to be sure and not just go by tests.
I’m sure eventually someone will dream up an even fancier system, so I guess you have to think of your Enneagram subtype as a work-in-progress.