Conditionally hide scene

...in the past, I used custom navigation buttons for other courses, including courses with only one language, because 1) the extra work involved in creating the triggers, adjusting states etc. delayed development time and 2), the navigation buttons took up valuable slide real estate...

Basically this is what you need.
const listElements = document.querySelectorAll('li div.cs-listitem.listitem');

   for(var i = 0 ; i < listElements.length; i++){
   listElements[i].id = 'list_'+i;
   console.log("list "+i);
   if(i > 4){
   listElements[i].style.visibility="hidden";
   }
   } 

Depending on the exact setup of your project you need to figure out which of the listitems, as the menu in Storyline is just a <li> you want to hide.

Here you can see a working sample.
https://360.articulate.com/review/content/716c1463-079c-4b71-90db-fb59ede46e4f/review

And attached my sample.

As in my sample you can switch languages/li-items, there is an extra line to show all li's.

Kind regards,
Math

Thanks for the reply. Unfortunately my skills at JavaScript are next to nil and I don't really understand the code... I'm the VBA kind of guy. 

If you know VBA, javascript is a piece of cake :-)
And Javascript is the only solution for this in Storyline.