To add/remove profanity words go to the Class Defaults of the BP_ChatMessage search for Profanity Words, here you can add your words that will be filtered out by pressing the + button. Keep in mind that it will filter out these letters even if they are a part of another word. The below image are the default words you can add as many more as you like.

Players can then enable or disable Profanity Filter in their social settings, this is the cog wheel icon on the chat window.