How to set a module as "visited" once complete the scene\module and going back to the initial landing page?

This post describes how to program a custom menu slide: TIP: Create a Custom Menu Slide - Articulate Storyline Discussions - E-Learning Heroes 

You could use the basic instructions to change the state of your buttons based on whether or not the user completed the corresponding scene (module, topic, or whatever you want to call it).

• Don't use the built-in Visited state for your button. As you've seen, an object with a Visited state will automatically change to that state when it is clicked.
• Instead, add a custom state. Then use a trigger that changes the object to that state after the user finishes the corresponding scene. That would be tracked with a T/F variable (as described in the post). 

If you don't already know how to use trigger conditions and variables, it's worth it to learn. They provide the real power in Storyline. Here are some User Guide articles to get you started: 

• https://community.articulate.com/series/articulate-storyline-360/articles/articulate-storyline-360-user-guide-how-to-work-with-triggers#conditions
• https://community.articulate.com/series/articulate-storyline-360/articles/articulate-storyline-360-user-guide-how-to-work-with-variables