Contextual Alternates without the randomness

I need to combine my letter with special alternates, not the random ones. Does anyone know how I can do this? Means… I have 8 versions of my a and 8 versions of my b etc. But I need to combine the 4th a with my 6th b, my 3th a with my 8th c etc. I know it will be hard work to combine every letter with each other, but first I need to know how I can combine them.

Greetings Kira

There is a tutorial about this: