How to make Custom House Have Dynamic COA

I am playing as a High Valyrian House in Elyria, and I wanted to make the COA i have for them be considered a dynamic coa, how would I go about doing this as I saw there was a reddit post a few years ago describing how to add a dynasty to the Dynamic COA list but it dosnt say how to turn a ruler desinged dynasty into a Dyanmic COA and also keep the COA i made in the ruler Desinger. if anybody could help with that it would be much appreciated.