You can also use the Emblem button to add an additional symbol on top of the shield. The CoA Editor allows you to choose from a list of predefined templates and layers, and change their colors and positions. The simplest way is to use the in-game CoA Editor, which is available if you have the Customization Pack DLC or the Ruler Designer DLC.
There are several ways to create or modify a CoA in CK2.
