For example, the last 4 ingredients should be mixed together independently before folding in to the base.

Isn't that indicated by the combination of rows?

I like this chart. It even allows for ~~multithreaded~~ multi-person baking, because the combination of rows indicates where processes are merged (and need to be done).

Edit: I may be dumb. A mix step is missing below the mix block of the other ingredients, but it could easily be included.