I did a search but the word parallel makes this really makes it challenging to find the answer. I have once had parallel subprojects happen in one of my main projects, but I cannot find out how to make that split (i.e. I don’t know how it happened the first time). How do I do that?
Do you mean change from a Sequential to a Parallel?
Only works on a task that has sub-tasks (then all child tasks take on that attribute).
Highlight your task, then on the Inspector there should be two (lower level) or three (top level) options: Sequential, Parallel, or Single Action (top level only).