Storyboard flow
 

Let's say I have an Event A in my storyboard.
From this event the PC's receive a task which goes to Event B
Once they complete this Event B and return to Event A which triggered Event B then they are given information which now would lead the to Event C

How do you connect this workflow within the storyboard so when I'm looking at it I know Event C can't be triggered until Event B is completed.

Do I create 2 plot points, Event 1a and 1b where both are linked to the same content.

Or do I split the content into 2 separate events themselves?

I would have Event A and B linked to C and put remark in the GM section of event C that it can be accessed from A only if B is completed.
The link from B to C is to show that in the main story it is related. There are no “dotted lines” for the links, so the comment is my best suggestion here.

Also you can just go A > B > C to keep it clean and add comments and link to different scene.