Custom code to generate a dynamic page detail

Hi!

I have a very similar problem as @Javier_GrowthLab. I am trying to create a dynamic menubar on the left side of the screen was an active scrolling site on the right side(majority of screen).

I would love to access the code used for this. Can @artur please help me?

Here is the design I am trying to replicate:

I posted a discussion on a separate page if it is easier: create a dynamic menu bar

Thank you,
Ilan