Tracking Completion of Branches

It sounds like you have a custom menu slide where the user selects each branch. You want to let them go through the branches in any order, but they must complete both. 

One way to do that is to use T/F variables to track whether the user has completed each branch or not. That's as easy as starting with a T/F variable for each branch with a default value of False. Add a trigger to the last slide of the branch that changes the associated T/F variable to True.

Then, on your custom-menu slide, you could do either of the following:

• Add a "Complete course" trigger that runs when the timeline starts with the condition that both of the variables = True.  Note: If you use this option, I suggest you also show a you-completed-this-course message when the variables = True.

or

• Add a button with an Initial State of Disabled or Hidden. That button should have a trigger to jump to an end-of-course slide with a "Complete course" trigger. A separate trigger on the custom-menu slide should change the state of that button to Normal when the timeline starts with the condition that both of the variables = True. 

This post has more info about custom menus, plus a demo file: TIP: Create a Custom Menu Slide - Articulate Storyline Discussions - E-Learning Heroes 

Here's the User Guide info about trigger conditions: https://community.articulate.com/series/articulate-storyline-360/articles/articulate-storyline-360-user-guide-how-to-work-with-triggers#conditions  

Here's the User Guide info about variables: https://community.articulate.com/series/articulate-storyline-360/articles/articulate-storyline-360-user-guide-how-to-work-with-variables