How can i make a firing pattern for my bullet hell?

Hi everyone! I am currently creating a bullet hell game and i've implemented a "pattern" for the bullets that I want the boss to spawn. Here is the code:

I know it's very basic and for that reason I would like to create a some more advanced pattern. On youtube I found this video, and I would like to be able to implement the attacks N°6, N°8, N°16 and/or N°25:

Thanks in advance ~ ;u;