You know how you can have multiple patterns on banners? Well now you can customize your armor just as much too!
The mod allows you to put multiple trims on your armor at the same time instead of 1 at a time. You can customize the limit using the gamerule maxTrimStack, which is 32 by default, but can go up to 1000 (which is kind of overboard).
So go out and make your armor look fabulous!